S.DAYIS.PUBLISHER.DETRQIT. 






LIBRARY OF CONGRESS. 

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UNITED STATES OF AMERICA. 



1 



THE STUDENTS 



Manual of Histology 



FOR THE USE OF 



Students, Practitioners and Microscopists, 



-BY- 



Chas. H. Stowell, M. D., 

Assistant Professoi of Physiology and Histology, and the Instructor in the Physiological 
Laboratory of the University of Michigan. 



' 



ILLUSTRATED BY ONE HUNDRED AND NINETY-TWO ENGRAVINGS. 






BF 






DETROIT: 

Q-co. S. X5a.A.-ic, 3P"UL"bl±sQa.er. 
1881. 






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Entered according to the act of Congress, in the year 1881, by 

GEORGE S. DAVIS, 

In the Office of the Librarian of Congress, at Washington, D. C. 



■■ 



PREFACE. 



HISTOLOGY has made such rapid advances within the past few 
years — not only regarding its place as a part of the science ~of 
medicine, but also regarding the new facts discovered by working 
microscopists of both continents, — that a manual of this character, 
bringing the subject down to the present time, will, we trust, meet 
the wants, alike of the student, physician and microscopist. 

This manual is not intended to supercede either the large text- 
book of Strieker or the complete atlas of Klein or other similar 
works. While these works are necessary and invaluable to the 
teacher, yet it has been apparent to us for some years that they 
were altogether both too full and expensive to make them compan- 
ions of the student ; and now that our laboratories are so general 
that nearly every medical student studies the microscopic structures 
of the various tissues, even the admirable compend of Frey fails 
to supply the want, viz., necessary directions for preparing and 
preserving. 

We have endeavored, in this volume, to condense the descrip- 
tions as much as possible without injury to its completeness or 
accuracy. 

Of course there are many subjects concerning which our best 
students and writers materially differ, and as it would far exceed 
the limits of this work to engage in discussions, we have given in 
such cases, either those results most generally received or those 
to which most authority is attached, with, perhaps, the author's own 
particular views added. 

The 'laboratory work' is, by no means, exhausted, nor is it 
even full. Those methods are given which are most familiar and 
which have proved the most satisfactory in our hands. 
l^ZZ So far as our knowledge goes these are the best methods known, 
yet others may be as good and it would not be surprising if some 
were found better. 

We have taken some care to discover who was the original 
owner of the drawings we have taken from other books. Wo have 



PREFACE. 



found nearly everyone of them in several works and no credit 
given to anyone. When we were not positive, credit was given to 
to the author of the work in which the drawings were found. 
Credit should be given to Beale for figure 122. The re- 
maining drawings were all carefully and accurately made from 
specimens prepared by us, nearly all of which are now in our 
possession. We believe they can be fully relied upon as correct. 
The magnifying power used is given in each case, therefore when 
the size of any object is not given in the text it can be readily 
ascertained by dividing the size of the figure by the number of 
diameters it is magnified. The magnifying power was acertained 
by measuring the micrometer (Roger's) lines at ten inches from the 
eye-piece. 

The subject of the first chapter can be treated but briefly. To 
obtain anything like a complete knowledge of this subject it will be 
necessary to consult some of the following works : "Microscopical 
Technology," Dr. Carl Seiler ; "The Microscope and Microscopical 
Technolog}^" Frey ; "How to use the Microscope," Beale. 

Our facilities for obtaining tumors have been ample, and their 
study has taken much of our time. 

The illustrations given are from specimens of our own prepar- 
ing and they convey as accurate an idea as possible of the appear- 
ances of these growths as seen under the microscope. 

The concluding chapter on the principal starches is introduced 
because these grains are so frequently encountered in general work, 
and because the physician or microscopist is so often called , upon 
to examine a specimen with reference to their presence. 

I am especially indebted to my former assistant, Dr. D. N.^De 
Tarr (now of the New York State Museum) for most valuable assist- 
ance both in the preparing and in the producing on paper of 
many of the specimens. For the neatness and tact displayed in 
the production of the book we all are alike grateful to the publisher. 

Chas. H. Stowell. 

"Physiological Laboratory," 

University of Michigan. 
March, 1881. 



CONTENTS. 

Preface, - - - - - - - - 3 

chapter 1. 
The Microscope, - - - - - - -11 

CHAPTER II. 

The Amoeba and the Cell, - - - - - -29 

CHAPTER III. 

Blood, - - - -. 38 

CHAPTER IV. 

Epithelium and Hair, ------- 62 

CHAPTER V. 

Connective-tissue Group, - - - 73 

CHAPTER VI. 

Teeth, ■-._.-■_ - - 90 

CHAPTER VII. 

Muscle, - . - - 98 

CHAPTER VIII. 

Blood-vessels, - - - - - - -112 

CHAPTER IX. 

The Respiratory Passages, - - -121 

CHAPTER X. 

The Salivary Glands and the Pancreas, - 130 

5 



6 INDEX. 

CHAPTER XI. 

The Pharynx, (Esophagus, Stomach and Intestine, - 134 

CHAPTER XII. 

The Liver, --------- 144 

CHAPTER XIII. 

The Kidney, - - - - - - - - 151 

CHAPTER XIV. 

The Lymphatics, ____--_ 162 

CHAPTER XV. 

Nerve Fibres and their Modes of Termination, - - 173 

CHAPTER XVI. 

The Spinal Cord, - - - - - - - 186 

CHAPTER XVII. 

The Brain, --------- 196 

CHAPTER XVIII. 

Testicle and Ovary, - - - - - - • _ - 203 

CHAPTER XIX. 

The Tongue, Skin, Lining of Nasal Cavity and the Ear, 214 

CHAPTER XX. 

The Eye, --------- 228 

CHAPTER XXI. 

Tumors, - - . - - - - - - - 246 

CHAPTER XXII. 

The Starches, -------- 268 



ILLUSTRATIONS. 

PIG. PAGE. 

1. Compound Microscope 12 

2. Eye-piece in Section 14 

3. Objectives 15 

4. Chromatic and Spherical Aberration 17 

5. Eye-piece Micrometer 19 

6. Camera Lucida 20 

7. Turn-table 22 

8. Microtome 23 

9. Injecting Apparatus 27 

10. Amoeba 30 

11. Amceba dividing 31 

12. Human Ovum 32 

13. Flattened, cylindrical and branched cells 33 

14. Fully developed cell 33 

15. Illustrating diminishing nuclei in cells 34 

16. Pus in epithelial cells 35 

17. An epithelial cell 36 

18. Red blood-corpuscles of human embryo 41 

19. Blood-cells from spleen pulp 42 

20. Human blood 48 

21. Blood corpuscles of nian showing nuclei 51 

22. Frog's blood 53 

23. Relative sizes of corpuscles of different animals 56 

24. Blood-crystals 57 

25. Effect of reagents on blood 59 

26. Pus 59 

27. Ciliated epithelium and goblet cells 64 

28. Epithelium from intestine 65 

29. Ciliated epithelium from uterus 67 

30 Saliva 67 

31. Pigmented epithelium 68 

32. Epithelium from back of hand 68 

33. Epithelium from the nail 69 

34. Human hair 69 

35. Cat's hair 70 

36. Human hair sac 71 

37. Transverse section of hair follicle 72 

38. White fibrous and yellow elastic tissue 74 

39. Connective-tissue cells 75 

40. Adipose tissue 76 

41. Pigmented connective-tissue cells W 

42. Hyaline cartilage 79 

43. Thyroid cartilage 7i> 

44. Transverse section of bone ^ Sl 

45. Longitudinal section of bone M 

7 



INDEX TO ILLUSTRATIONS. 



FIG. PAGE. 

46. Lamellae of bone 83 

47. Bone cells, highly magnified '. 84 

48. Fresh bone cells 85 

49. Sharpey"s fibres 85 

50. Cancellated bone 86 

51. Longitudinal section of tooth, enamel 90 

52. Transverse section of tooth 91 

53. Cementum and dentine 92 

54. Membrane of dental tubes 93 

55. Odontoblasts 94 

56. Transverse section of muscle 99 

57. Sarcolemma of muscle 99 

58. Striated muscle fibre 100 

59. Muscle fibre, 101 

60. Muscle fibre 101 

61. Muscle from human heart 103 

62. Muscle from diaphragm 104 

63. Muscle cells - 104 

64. Muscle cells 105 

65. Termination of muscle in tendon 107 

66. Trichinous muscle ION 

67. Fatty infiltration and degeneration of muscle 109 

68. Capillary vessel from mesentery 112 

69. Capillary vessels 113 

70. Capillaries from muscle of a cat 114 

71. Walls of an artery 115 

72. Capillaries of the stomach of a cat 116 

73. Capillaries of the villi of an infant 117 

74. Capillaries of human lung 117 

75. Capillaries in the kidney UN 

76. Capillaries of mucous membrane of intestine 118 

77. Capillaries of villi 119 

78. Formation of bronchi and pulmonary cells 121 

79. Lobule of human lung 123 

80. One-half of frog's lung 124 

81. Section of human lung 125 

82. Section of lung of young child 126 

83. Fragments of lung tissue 129 

84. Salivary tubes 131 

85. Submaxillary gland 132 

86. Section of gastric mucous membrane 135 

87. Horizontal section through fundus of stomach 135 

88. Peptic glands 136 

89. Fundus of a gland tube 137 

90. Transverse section of the ileum of an infant 139 

91. Vertical section of villus of small intestine 140 

92. Lieberkiihnian glands 141 

93. Transverse section of an hepatic lobule 145 

94. Hepatic and sublobular veins 146 



INDEX TO ILLUSTRATIONS. 



PIG. PAGE. 

95. Liver cells 147 

96. Biliary capillary 148 

97. Biliary capillary 149 

98. Biliary capillary 149 

99. Diagram of the formation of the uro-genital organ 151 

100. Section of a kidney 152 

101. Illustrating the pyramids of the kidney 153 

102. Vertical section through the medullary pyramids 154 

103. Glomerulus of a rabbit 154 

104. Capsule of a glomerulus 155 

105. Malpighian bodies and tubes of the kidney 156 

106. Section of an injected kidney 15S 

107. From kidney of the pig 159 

108. Vascular arrangement of the kidney 160 

109. Central tendon of the diaphragm 163 

110. Lymphatic canal 164 

111. Section of lymphatic gland 165 

112. Section of lymphatic gland 166 

113. Section through Peyer's patch 167 

114. Splenic artery with Malpighian bodies attached 168 

115. Section of spleen pulp 169 

116. Section of spleen pulp 170 

117. Medullated nerve fibres 174 

118. Varicose nerve fibres 175 

119. Axis cylinder 176 

120. Non-medullated nerve fibres 177 

121. Ganglia cells 177 

122. Ganglion cell from hyla : . . 179 

123. Showing division of nerve fibres ISO 

124. Muscle fibres from guinea pig 181 

125. Muscle fibres from frog 1S2 

126. End bulb from conjunctiva of man 183 

127. Pacinian corpuscle 184 

128. Nerve papillae from skin 1S4 

129. Sections of spinal cord of various animals 186 

130. Diagrammatic section of cord 1S7 

131. Sections of human cord 188 

132. Section of the cord of a dog 1S<) 

133. Nerve cells from cord of the ox 101 

134. Nerve cells from human cord 192 

135. Central canal of human cord 1 98 

136. Section of human brain i;)T 

137. Ganglia cells from brain jgg 

138. Vertical section of the testicle 20* 

139. Wall of a seminal tubule v?t>> 

140. Spermatozoa 20 r 

141. Spermatozoa, highly magnified -.w 

142. Section of cat's ovary 810 

143. Vertical section of an ovary 211 



INDEX TO ILLUSTRATIONS. 



FIG. PAGE. 

144. Graafian follicle 212 

145. Taste buds 215 

146. Cells from taste buds 216 

147. Cells from olfactory region of frog 217 

148. Epidermis 218 

149. Prickle cells 218 

150. Sudoriferous gland 219 

151. Cochlea laid open 221 

152. Membranous labyrinth 222 

153. Otoliths 223 

154. Diagram of auditory epithelium 223 

155. Rods of Corti 224 

156. Organ of Corti 225 

157. Transverse section of the eye 229 

158. Section of the cornea of a rabbit 230 

159. Corneal corpuscles 231 

160. Surface of human iris 232 

161. Connective substance of the retina 233 

162. Nervous elements of the retina 234 

163. Nervous elements of the retina 235 

164. Rods of the retina. 237 

165. Fibrillated covering of the rods and cones , 238 

166. Macula lutea and fovea centralis 240 

167. Layer seen from without 241 

168. Longitudinal view of fibres of lens 242 

169. Section through margin of rabbit's lens 343 

170. Fibroma 251 

171. Lipoma 252 

172. Myxoma 254 

173. Lymphoma 255 

174. Papilloma 258 

175. Adeno-Fibroma 259 

176. Spindle cells 259 

177. Myeloid ceUs 260 

178. Melanotic cells 261 

179. Large and small round cells 262 

180. Stroma of scirrhus 263 

181. Cells from scirrhus 264 

182. Stroma of encephaloid 265 

183. Colloid 266 

184. Epithelioma 267 

185. Potato starch 269 

186. Wheat starch 271 

187. Bean starch 272 

1S8. Corn starch 273 

189. Rice starch 274 

190. Oat starch 275 

191. Buckwheat starch 276 

192. Turmeric starch 278 



CHAPTER I. 



The Microscope. 

THE word 'microscope' is a compound of two Greek 
words, piikpoZ, a small thing, and akon^oD, to view. 

Microscopes may be ' divided into two general classes, 
simple and compound. In a simple microscope we look at the 
object directly, while in a compound microscope we look at 
the magnified image of the object. Thus the difference is 
purely an optical one, for a simple microscope may be much 
more expensive and complex than a compound one, although 
as a rule the opposite is true. 

In the simple microscope the object is seen in its natural 
position, but in the compound microscope the image is re- 
versed, or inverted. This may be obviated by placing in the 
body of the microscope a set of lenses termed the erector. 
Very soon, however, the student becomes familiar with this in- 
version, and is not annoyed in the least by it. 

The compound microscope consists essentially of an ob- 
ject glass, or objective, which magnifies the object, an eye- 
piece which magnifies the image formed by the objective, a 
mirror to reflect the light and mechanical appliances. 

The Stand of a microscope includes all the framework to 
which are attached the eye-piece and the objective. Stands are 
sold separately by many makers, although one or more eye- 
pieces usually accompany them. The purchaser is thus left 
free to make his own selection of objectives. 



THE STUDENTS MANUAL OF HISTOLOGY. 







(Cut one-third of actual size.) 



[Bausch and Lomb.] 



Fig. i. Compound Microscope. A, the base or foot; B, the body; C, the draw-tube; D, th« 
arm; E, the collar; F, the coarse adjustment ; G, the fine adjustment; H, the stage; I, the ob- 
ject-carrier, K, the diaphragm, i, the mirror; 2, the eye-piece; 3, the objective. 



THE STUDENTS' MANUAL OF HISTOLOGY. 1 3 

A stand usually consists of the following parts : 

The Base or Foot (Fig. i.) "A:" Of all the forms the tri- 
pod meets the most general approval. 

The Body, "B," that part to which the objective is at- 
tached. 

The Draw-Tube, "C," which slides within the body. 

The Arm, "D," a support for the body. This is usually 
broken by a joint in order that the instrument may be inclined 
as seen in the figure 

The Collar, "E," a tube surrounding the body. 

The Coarse Adjustment, "F," for coarsely focusing the 
instrument. 

The Fine Adjustment, "G," for more accurate work. 
This is one of the most desirable things about a stand and 
should be carefully examined by the purchaser. 

The Stage, " H," is that part upon which rests the object 
to be examined. 

An Object-Carrier, " I," is many times combined with the 
stage in order that the object may be more accurately and 
carefully moved about. Although not strictly necessary it is 
a great convenience. " Mechanical " stages are made for that 
purpose. 

The Diaphragm " K," is placed beneath the stage, pierced 
with different-sized openings, to regulate the amount of light. 

Several appliances are sometimes attached to the stand as 
aids to microscopical manipulation. It would be beyond the 
limits of this work to enter into their description or to mention 
the many accessories necessary to complete the outfit. 

The Mirror, " i," usually consists of two surfaces, a plane 
one which reflects the light feebly, and a concave one which 
concentrates the light upon the specimen. It is attached to a 
swinging bar beneath the stage in such a manner that light 
may be reflected from almost any quarter. On some stands it 
is so arranged that it can be thrown over the stage and the 



14 



THE STUDENTS MANUAL OF HISTOLOGY. 



light reflected on the top of an opaque specimen. This avoids 
the necessity of an extra condenser. 

The eye-piece, " 2 " consists of two glasses mounted 
in either hard rubber or brass. Midway between them is 
a diaphragm to cut off the outer rays of light. The eye-piece 
in most general use is known as the negative or Hughenian. 
In this eye-piece the convex side of the lenses is directed 
downward. The lens nearest the eye for this reason is called 
the eye-glass, and the one farthest from the eye, and nearest 
the field, is called the field-glass. 



c 



FIG. 2. Eye-piece in section, a, eye-glass; b, diaphragm; c, field-glass. 

The magnifying power of eye-pieces is designated by 
either numbers or letters. In this country letters are chiefly 
employed. The lowest power is known as " A" or No. 1 ; 
higher powers are known as " B " or No. 2, " C " or No. 3, 
and so on. The greater the magnifying power, the shorter 
will be the eye-piece. The short eye-piece, or the one with 
high power, is also known as the deep eye-piece ; the longer, 
or the one with less power, as the shallow eye-piece. One 
eye-piece, then, may be " A " or low, or shallow ; another may 
be " D " or high, or deep. 

As an eye-piece does not magnify the object itself but the 
image of the object produced by the.objective, it will be seen 



■BHHHI 



THE STUDENTS MANUAL OF HISTOLOGY- 



how any imperfection in the objective will be augmented. 
High eye-pieces should be used only with fine first-class 
objectives. 

The objective, "3," is usually composed of one or more 
systems of glasses. A system consists of two or more glasses. 
It is not made of a single glass because the powers of refraction 
and dispersion are not equally united in any single refracting 
medium. That is, in the same power of refraction one medium 
may give a much greater deviation to the colored rays than 
another. 

Crown and flint glass act with regard to each other in such 
a manner that if a crown glass lens be united with a 
flint glass lens, the refraction of the former is lessened 
by the dispersive action of the latter, while the color 
dispersion of the former is neutralized by the opposite action 
of the latter. Spherical aberration may be largely remedied by 
this same combination. The lenses are firmly cemented 
together by Canada balsam or Dammar. The glasses thus 
united constitute a system, and in Fig, " 3," three of these 



^ 





FIG. 3. A, Achrom 
C, objective wi 



latic objective of three systems; B, objective with high angle of aperture 
-vith low angle of aperture. The angle of aperture is the angle c a c. 



systems complete the objective. These systems are mounted 
in either brass or hard rubber, which at the upper end is 
provided with a screw of standard size. Such a sized 
screw is called a " Society Screw " and will fit in the body 
of any first-class stand. 



i6 



THE STUDENTS MANUAL OF HISTOLOGY. 



An objective should possess the following good qualities : 
Defining power. 
Resolving power. 

Freedom from spherical aberration. 
Penetrating power. 
Freedom from chromatic aberration. 
Flatness of field. 
Working distance. 
Defining power is without question the most important 
quality to be sought in a lens. Its presence makes the objec- 
tive of the utmost value, and its absence renders it simply 
worthless. 

Defining power gives a clear, distinct and sharply cut out- 
line. Its absence is denoted by haziness, indistinctness and 
want of clearness. 

Resolving power enables closely approximated markings 
to be seen distinctly. While defining power shows the outline 
of a specimen well, resolving power enables the observer to de- 
tect the most intricate structure on its surface. 

Spherical aberration exists when the peripheral and cen- 
tral rays do not actually reunite in a point. Those rays 
passing near the periphery, being more strongly refracted, 
come to a focus sooner than those which pass through the 
central portion. Now if some parts of a lens bring the rays 
to a focus sooner than other parts, they must magnify more, 
thereby distorting the figure. This is found to be the case 
with all objectives having spherical aberration, causing what 
is known as "aberration of form." 

With penetrating power we look deep into the structure of 
the object. 

Chromatic aberration exists when a ray of light is not 
refracted as a whole, but is decomposed into rays of various 
colors, which are refracted in different degrees, forming a spec- 
trum. All objects examined now are seen fringed with colors 



THE STUDENTS MANUAL OF HISTOLOGY. 1 7 

An objective is said to be " achromatic " when it is nearly, if 
not quite, free from this aberration. 

It is impossible to perfectly remedy these two aberrations, 
but by the use of the two kinds of glass mentioned above, they 
are nearly obviated. Objectives thus made are said to be 
" corrected." 




1r 

— c 



B 




FIG. 4. A, chromatic aberration; a, c, rays oT white light; v, violet rays; r, red rays. 
B, spherical aberration. 

A Field includes all that is presented, to the eye through 
the microscope. It is said to be flat when all parts of it are in 
focus at the same time. An objective with good defining power 
is very liable not to have a flat field, and a perfectly flat field is 
usually associated with poor defining power. Defining power 
should never be sacrificed for flatness of field, since with a 
good, fine adjustment the latter is easily remedied, while noth- 
ing can restore the former. 

Working distance is the distance between the front glass 
of the objective and the point in focus. Some manufacturers 
make objectives with a large working distance without 
materially affecting their defining or magnifying power. For 
many purposes such objectives are of groat value. For a dis- 
cussion of the vexacious question of " angular aperture " we 
refer our readers to works on microscopical technology or to 



l8 THE STUDENTS MANUAL OF HISTOLOGY. 



many articles in the various microscopical journals. The 
usual definition is this : 

Angle of aperture is the angle formed by two lines extending 
from the point in focus to the opposite sides of the aperture of 
the objective. While one school claims that a high angle has 
great resolving and poor penetrating powers, another school 
earnestly urges that both can be combined in the same objec- 
tive. 

Immersion objectives are those that require a drop of 
liquid between the end of the objective and the cover glass. 
Water is generally employed for this purpose, although glyce- 
rine, on account of its greater density, is sometimes used. 
By employing a liquid in this way the glass surfaces of the ob- 
jective and cover glass are, to a certain extent, extinguished 
and thus a considerable loss of light prevented ; at the same 
time the refraction of the rays of light at the upper surface 
of thereover glass is very much diminished, so that many more 
rays of light pass into the microscope. The specimen is then 
better illuminated, and also better defined. 

Objectives are numbered according to their magnifying 
power. In this country the system is different from that 
abroad, where they are numbered i, 2, 3, 4, 5, etc. Here an 
objective is known as an inch, one-half inch, one-fqurth, one- 
eighth, one-thirtieth, etc. These terms refer solely to the mag- 
nifying power. For instance, a one-fourth inch objective has 
the same magnifying power as a single lens whose focal distance 
is one-fourth of an inch. 

Each microscope should have with it a micrometer. 

Nothing can be more convenient or useful than a good 
eye-piece micrometer. Knowing the value of the spaces 
to which it is ruled, objects can be accurately and quickly 
measured. Of course, the value of these spaces will depend upon 
the objective used and the length of the tube of the micros- 
cope. By always using the draw tube fully extended the length 
of the tube will be fixed, and with the aid of a stage micrometer 



THE STUDENTS MANUAL OF HISTOLOGY. 19 



ruled 100, 1000, 2000 lines to the inch, the value of the spaces 
of the eye-piece micrometer for the various objectives is 
reckoned once for all. This is done in the following manner : 
Bring in the field the lines of the stage micrometer 1 ( } oli - of an 




FIG. 5. Eye-Piece Micrometer. (Increased one-third.) 

inch apart ; place the eye-piece micrometer in its proper place in 
the eye-piece ; notice how many spaces of the eye-piece micro- 
meter cover one space on the stage micrometer. Using the % 
inch objective and the " C " eye-piece, we will assume that five 
spaces of the eye-piece micrometer cover one on the stage mi- 
crometer. Then one space on the eye-piece micrometer re- 
presents the joW °f an mcn - Now remove the stage micro- 
meter and place in the field a specimen of blood, for instance, 
a white blood corpuscle is. seen just to fill two spaces in the 
micrometer. It is then the go g o0 of an inch in diameter. 

To determine the magnifying power of a microscope, it is 
inclined until the eye-piece is ten inches from the table. The 
lines of a stage micrometer are then accurately focused. By 
means of a "Camera Lucida" or "Neutral tint glass reflector" 
(Fig. 6), the magnified image is thrown upon a sheet of paper 
resting on the table and directly beneath the eye-piece. The 
lines are traced with a pencil while the eye is in the position 
noted in the figure, and their distance apart measured with a 
scale. This distance is divided by the distance between the 
lines on the stage micrometer, and the result will be the 
number of diameters the instrument magnifies — not the num- 
ber of times or areas, which would be the square of the 
-diameters. Or the following method : Place a scale in front 



THE STUDENTS MANUAL OF HISTOLOGY. 



of and ten inches below the eye-piece. By looking in the 
instrument and keeping both eyes open, the lines of the stage 
micrometer can be seen resting on the scale, when their 
distance apart can be noted. Divide this distance by that 
between the lines on the micrometer, and the number of 
diameters will be given. 

Having no eye-piece micrometer, the size of any object is 
obtained in the following way ; Assuming our microscope to 




i 

FIG. 6. Camera Lucida, or Neutral Tint Reflector. (Bausch and Lomb.) 

magnify 500 diameters, the specimen to be measured is sub- 
stituted for the stage micrometer, and its image thrown down 
on the paper as were the lines of the micrometer, and its size 
measured with a scale. This measure is divided by the mag- 
nifying power of the instrument. Thus a red blood corpuscle 
appears on the paper Jfc of an inch in diameter. It has been 
magnified 500 diameters. Its true size then is jfo of its 
apparent size, viz. 40 1 00 of an inch. 



THE STUDENTS MANUAL OF HISTOLOGY. 2 1 

A microscope is said to be " in focus " when the specimen 
is seen to the best advantage. For the higher powers the fol- 
lowing rule should be observed : Incline the head until the eye 
is on a level with the stage. With the coarse adjustment place 
the objective very near the cover glass, within its focal length. 
Then, while looking in the microscope, focus up. If this rule 
be carefully observed, the breaking of cover glasses and the 
destruction of specimens will be materially diminished. 

For general microscopical work daylight is to be preferred. 
Not strong direct sunlight, which is only useful under special 
circumstances, but such an even, steady light as can be found 
by a window looking to the north. Nothing can take the place 
of this northern light, both when the sky is clear, and when, 
best of all, the sunlight is reflected from a white cloud. While 
gas-light and lamp-light are inferior to daylight and weakening 
to the eyes, direct sunlight is positively injurious. 

Transparent objects may be viewed by either direct or re- 
flected light. 

When the light passes directly through the specimen and 
microscope without having been reflected by the mirror, it is 
said to be direct. 

If the mirror be so placed that the reflected rays are in the 
optical axis of the microscope, the light is said to be central, 

If the mirror be turned to one side so that the rays pass 
through the object at an acute angle, oblique light is obtained. 

In the care of the microscope the following practical hints 
may not be out of place : 

When removing from, or placing on the stage a specimen, 
if the higher powers have been used, always raise the body of 
the instrument. 

It is rarely necessary to clean a good microscope. 

Use soft, chamois to clean, and camel's hair brushes to 
dust. 

Remove balsam, etc., from objectives by slightly moisten- 
ing the chamois in turpentine and carefully wiping it off. 



22 



THE STUDENTS MANUAL OF HISTOLOGY. 



Avoid handling the instrument. 

Carry it by the arm. 

Always clean immersion objectives thoroughly, and imme- 
diately after using. 

When not in use, keep the instrument in its case or under 
a bell jar. 

However ; better let the instrument wear out rather than 
rust out. 

For practical work a good microscope need have but two 
eye-pieces of different powers, and a i in. and % in., or £i 
in. and -J- in. objectives. 




FIG. 7. Turn-Table. iR. and J. Beck.) 

The beginner will need a pair of fine dissecting forceps, 
curved scissors, a knive or two, a few needles, a razor flat on 
one side and concave on the other for making sections, a few 
camel's hair brushes, chamois skin, glass slides and cover 
glasses. These, with the following list of twelve reagents, will 
complete the necessary outfit. Other reagents and instruments 
will be added as their need becomes manifest. Many of them, 
however, the ingenuity of the worker, who is weaker in his 
pocket than in his head, will extemporize. Notably a " turn 
table" and "microtome." (Fig. 7 and 8.) 



THE STUDENT S MANUAL OF HISTOLOGY. 



23 





LIST OF 


REAG 


I. 


Normal saline solution, 


7. 




% p. c. solution. 


8. 


2. 


Glycerine." 


9- 


3- 


Alcohol. 


JO. 


4- 


Ether. 


II. 


5- 


Acetic acid. 


12. 


6. 


Iodine solution. 





Canada balsam. 

Carmine staining. 

Hematoxylin. 

Oil of cloves. 

Dammar. 

White zinc cement. 




FIG. 8. Microtome. (R. and J. Beck.) 

For anything like a complete list of the various reagents, 
injecting and staining mixtures, and the methods of preparing 
them, the reader is referred to special works on those subjects. 
We append a few formulae in general use. 

BEALE'S PRUSSIAN BLUE, FOR TRANSPARENT INJECTIONS. 

Common glycerine, ----- 1 ounce, 
Spirits of wine, ------ 1 ounce, 



24 THE STUDENTS MANUAL OF HISTOLOGY. 

Ferrocyanide of potassium, - - 12 grains. 

Tincture perchloride iron, - - 1 drachm. 

Water, - -4 ounces. 

The ferrocyanide of potassium is to be dissolved in one 
ounce of the water and glycerine, and the tincture of iron 
(muriated tincture of iron) added to another ounce. These 
solutions should be mixed together very gradually and well 
shaken in a bottle. The iron being added to the solution of 
the ferrocyanide of potassium. When thoroughly mixed, the 
solutions should produce a dark blue mixture, in which no 
precipitate or rlocculi are observable. Next the spirit and the 
water are to be added very gradually, the mixture being con- 
stantly shaken in a large stoppered bottle. In cases, in which 
a very fine injection is to be made for examination with the 
highest powers, half the quantity of iron and ferrocyanide of 
potassium may be used. 

BEALE's ACID CARMINE INJECTING FLUID. 

Carmine, - ----5 grains. 

Glycerine, with 8 or 10 drops of acetic or 

hydrochloric acid, ----- 3^ ounce. 

Glycerine, ----------- 1 ounce. 

Alcohol ------------ 2 drachms. 

Ammonia, ----------- a few drops. 

Mix the carmine with a few drops of water and, when well 
incorporated, add about five drops of liquor ammoniac To 
this dark-red solution about half an ounce of the glycerine is 
to be added, and the whole well shaken in a bottle. Next, 
very gradually pour in the acid glycerine, frequently shaking 
the bottle during admixture. Test the mixture with blue lit- 
mus paper, and if not of a very decidedly acid reaction, a few 
drops more of acid may be added to the remainder of the gly- 
cerine, and mixed as before. Lastly, mix the alcohol and wa- 
ter very gradually, shaking the bottle thoroughly after adding 
each successive portion till the whole is mixed. 



■H 



THE STUDENTS MANUAL OF HISTOLOGY. 25 

STAINING MIXTURES. BEALE'S STAINING CARMINE, FOR STAIN- 
ING GERMINAL MATTER. 

Carmine, -- 10 grains. 

Strong-liquor ammonias, - - y 2 drachm. 
Price's glycerine, 2 ounces. 

Distilled water, ------ 2 ounces. 

Alcohol, Yz ounce. 

The carmine in small fragments is to be placed in a test 
tube, and the ammonia added to it. By agitation and with 
the aid of the heat of a spirit lamp, the carmine is soon dis- 
solved. The ammoniacal solution is to be boiled for a few 
seconds, and then allowed to cool. After the lapse of an hour, 
much of the excess of ammonia will have escaped. The gly- 
cerine and water may then be added and the whole passed 
through a filter or allowed to stand for some time and the per- 
fectly clear supernatant fluid poured off and kept for use. 

HEMATOXYLIN. 

Make a saturated solution of crystallized calcium chloride 
in 70 per cent, alcohol. Shake and let stand. Add alum to 
excess. Shake well, let stand, and then filter. Make a satu- 
rated solution of alum in 70 per cent, alcohol. Add this to 
the above filtrate in the proportion of 8 to 1. To this mixture 
add drop by drop a saturated solution of hematoxylin in ab- 
solute alcohol until it has a somewhat dark purple color. 
Too deep staining can be removed by placing the section in 
dilute acetic acid. 

ANILINE BLUE-BLACK. 

Dissolve 5 grains of aniline blue-black in 100 c. c. of wa- 
ter. Dilute with water to any strength required. 
The following arc useful for 

MOUNTING MEDIA. 

Canada Balsam. 

Canada balsam to be used without heat. Prepared as 
follows : Heat some of the balsam over a sand bath until it is 



26 THE STUDENTS' MANUAL OF HISTOLOGY. 

hard when cold. Then dissolve it in a small quantity of ben- 
zole. To mount in Canada balsam the specimen is thoroughly 
saturated with alcohol. The excess of this removed with 
strips of cut blotting paper and oil of turpentine added. As 
soon as the section has become saturated or cleared the excess 
of oil is removed and the balsam added. 

Dammar. This is a great favorite with most histologists. 
It renders the tissues more transparent than balsam and is a 
convenient fluid to handle. It is prepared as follows : One 
half ounce each of dammar resin and gum mastic is dissolved 
in 3 ounces benzole and filtered. To mount a section in dam- 
mar, it is first left in alcohol, than transferred to absolute al- 
cohol until no water is in the section. The excess is removed 
by blotting paper and the oil of cloves added. Here it is al- 
lowed to remain until transparent. If it does not clear in a 
short time, in all probability the alcohol did not entirely re- 
move the water. Alcohol should be added again and allowed 
to remain longer on the specimen. Adding the oil a second 
time will doubtless clear up the section completely. Then re- 
move the excess of oil with blotting paper and add a drop or 
two of dammar and cover with thin glass. 

If glycerine or other fluid mounting medium be used, it 
will be necessary to make a cell in which can be placed the 
fluid and specimen. Cells are made with either of the follow- 
ing cements : Gold size, Brunswick black, White zinc. The 
border may be oval, square or circular, — if circular, a turn- 
table is employed in order that the circle may be true and sym- 
metrical. This soon hardens and forms a firm support for the 
cover glass, the edge of which should come just to the centre 
of the border. An extra layer of cement is now added, one- 
half of which reaches on the cover glass and the other half on 
the glass slide. 

For embedding mixtures the following are especially re- 
commended : 



THE STUDENT S MANUAL OF HISTOLOGY. 



27 



Solid paraffin, 3 parts 
Cocoa butter, 1 part 
Hog's lard, 3 parts 

Solid paraffin, 2 parts 
Cocoa butter, 1 part 
Spermaceti, 1 part 



Solid paraffin, 3 parts ) 
soft. Cocoa butter, 2 parts >- hard. 
Spermaceti, 1 part ) 

Paraffin, 2 parts ) transp't and 
harder Vaseline, 1 part [ easy to cut. 




FIG. 9. Injecting Apparatus. 

For further information on these subjects the reader is re- 
ferred to Beale on "How to Work with the Microscope," 
" The Microscope in Medicine," or to the admirable work of 
Frey's, "The Microscope and Microscopical Technology." 



28 THE STUDENTS' MANUAL OF HISTOLOGY. 

Figure 9 illustrates a cheap injecting apparatus, a repre- 
sents a pail partly filled with water, which can be raised or 
lowered, to regulate the pressure, by fastening one end of a 
cord to the handle of the pail and then passing the other end 
over a pulley fastened to the ceiling of the room ; b is a bottle 
with an air-tight fitting cork, pierced by two short glass tubes ; 
c is a bottle partly filled with the injecting mixture. Through 
the cork of this bottle are two glass tubes, one of which is 
short, while the other reaches very nearly to the bottom of the 
bottle , d is a brass nozzle with a stop-cock ; r, is rubber tub- 
ing, which unites the different parts as seen in the figure. A 
y-shaped glass tube can be inserted midway in the rubber tube 
between the two bottles, so that two bottles of the injecting 
mixture can be attached to the one large bottle, b, which is 
empty at first. A third glass tube can be placed in the cork 
of the bottle c, which can be united by rubber tubing to a U 
shaped glass tube partly filled with mercury, and thus the 
amount of pressure obtained. By raising the pail, the water 
descends the rubber tubing and compresses the air in the 
bottle b. The air is forced through the middle piece of rubber 
tubing and presses on the top of the injecting mixture in the 
bottle c, which is forced up the glass tube, along the rubber 
tube to the canula, and into the animal or organ to be injected. 




CHAPTER II. 



The Amoeba and the Cell. 

LOW down in the scale of animal life are found minute organ- 
isms of variable size inhabiting stagnant water, mud, and 
water in which animal matter has been infused and exposed 
to the direct rays of the sun. They have the appearance of a 
particle of the white of egg, clear and transparent, perhaps 
slightly granular, quite fluid in the centre and of firmer con- 
sistency towards the periphery. 

They are especially remarkable for their incessant and 
rapid changes of form, causing them to move about, but not in 
any particular direction. Their movements are effected by a 
flow of their protoplasm, causing them to thrust out prolon- 
gations, known as pseudopodia. The dense exterior we know 
as the ectosarc, the more granular fluid interior, the entosarc. 
In some amoebae there appears a clear spot which dilates to a 
certain extent, then contracts rapidly and disappears, to reap- 
pear again with tolerable regularity. This is the contractile 
vesicle. It seems to serve two purposes, first, as a pump to 
force water into and out of the body, and second, as a means 
of procuring food, for when dilated to its full extent it will 
sometimes contract with such vigor as to break through the 
ectosarc and cause its contents to rush out into the liquid in 
which it lies. It then dilates, causing a strong suction force, 
which draws in a certain amount of water and with the water, 
infusoria, entozoa and vegetal forms, the food of our amoeba. 

A nucleus and nucleolus are occasionally scon. 

29 



3° 



THE STUDENTS MANUAL OF HISTOLOGY. 



The first thing noticed in examining one of these little 
animals is, it is contractile. Its peculiar amoeboid movements, 
its flow of protoplasm, are identical in their fundamental na- 
ture with the movements occurring in a muscle during its con- 
traction. The second is, it is irritable and automatic. If a 
foreign body be brought in contact with an amoeba when it is 
•at rest, movements result. These movements are not passive 
in their nature, proportionate to the force employed, but are 
the result of an explosion of the energy of its living matter. 
Rarely does one see the amoeba at rest. It is almost con- 
stantly changing its form, 
not from external stimuli, 
but from changes of its 
substance, the cause of 
which lies within the body 
itself. The marked feat- 
ures of nervous tissue are 
its irritability and auto- 
matism. The third is, it 
is secretory and excretory. 
Besides the method de- 
scribed above it will be 
noticed that our amoeba 
has another way of procuring food, — by extending around 
it its pseudopodia until the particle is completely surround- 
ed by the living matter. Here the foreign body remains 
for a time. If it be suitable for food it soon becomes changed 
into material like the mass surrounding it, — into " amoeba 
stuff." Part of it may be changed and the remainder thrown 
off as excrementitious matter or the whole may be served in a 
similar manner. If all the particle be not assimilated then the 
amoeba simply moves away by its flow of protoplasm and 
leaves it behind. There must be chemical products present 
for the purpose of dissolving and effecting changes in this 
raw new material taken as food. These must be regarded 




FIG. 



nucleus ; 
vacuole. 



b, foreign bodies 



THE STUDENTS MANUAL OF HISTOLOGY. 



3 1 



as secretions. Our amceba is certainly excretory. In man, 
the digestive, urinary, and pulmonary tracts, and the epithelia 
represent this physiological property of the amceba. 

The fourth" is, it is metabolic. Constantly undergoing 
chemical change. Certain cells in the human body are 
specially reserved for carrying on chemical changes. Their 
material is derived from the blood and their products are 
finally returned to it. Such cells are the fat cells, liver cells, also 
the lymphatic and ductless glands, and in one sense, the blood. 
The fifth is, it is reproductive. After attaining a certain 
size or living a longer or shorter life, it may by division 
resolve itself into two parts, each of which is capable of living 
as a complete unit. The amceba divides by becoming 
constricted in its centre, by its protoplasm flowing in opposite 

directions, or by a 
pseudopodium detach- 
ing itself from the 
body of the cell. Cer- 
tain cells are set apart 
in the human body for 
the accomplishment of 
this purpose. Such col- 
lections of cells are the 
ovary and the testis. 
Man, then, is but a 
federation of amcebi- 
form units. Certain of these units have been exclu- 
sively set apart for the manifestation of certain of 
the properties of protoplasmic matter. These groups have re- 
ceived the name of "tissues." With this grouping there has 
come a change in structure in order that the part might better 
perform its function. At one period in the history of these 
cells they were as simple as our amoeboid unit, in fact, for that 
matter, at an early period in the history of every life the whole 
being, the embryo, was but a mass of units as simple in their 




FIG 



Amceba dividing, 



32 THE STUDENTS' MANUAL OF HISTOLOGY. 



structure as the amceba. Some cells remain in this amoeboid 
condition in the body for a considerable time ; such cells are 
the mucous and pus corpuscles, and the white corpuscles of 
the blood. 

At a bound, then, we pass from this low creature to the 
highest to find that the tissues of the latter are but collections 
of the former. So a tissue is chosen and with the aid of the 
knife and needles its parts are for a time successfully sep- 
arated. 

But at last a period arrives when even this will not 
answer, and we turn to the microscope to find our tissue 
infinitely compounded of thousands of the smallest elements. 
To discover and to examine these constitute the science of 
tissues, or histology. 

While the cell existed as an amoeba it acted in an inde- 
pendent manner, but now that it is in the service of a unity of 
cells it is a subordinate and must conform itself to its sur- 
roundings. 

Each cell in the body then is a 
living individual with an individual 
function. Some of these cells are 
very small, for we shall see that it is 
possible for five millions of them to 
be contained in a particle of the sub- 
stance of the body no larger than a 
cubic millimetre. While some are 

FIG. :2. Human ovum. a, vitelline 1.1 1 • c . •. 

membrane; b, viteiius; c, germinal so large they are nearly, if not quite, 

ves,cle ; d, germinal spot. ^^ ^ ^ unaided Qy ^ In shape> 

also, there is the greatest variation. First, there is the 
spheroidal cell, from which the bodies of all the higher 
animal have proceeded, the ovum. As a result of com- 
pression and adaptation come other cells, from the slender 
cylindrical to the flat scaly. Still other cells appear with 
branched processes growing from their bodies in oppo- 
site directions. There exists, then, every variety of shape 




THE STUDENT S MANUAL OF HISTOLOGY. 



33 




and form in the fully developed cells, although we shall see 
further on that early in their history they were all alike, simple 
undifferentiated bioplasm. In a well developed epithelial cell 
from the surface "of the tongue two parts are readily recog- 
nized. First, the nu- 
cleus, a round or oval 
body, occupying a 
small part of the cell 
near or in its centre, 
and, second, the part 
of the cell surround- 
ing this. 

In the alkaline so- 
lution of carmine 
(page 25) we possess 
an agent capable of 

FIG. 13. A, flattened epithelial cells; B, cylindrical cells; coloring the different 
C, branched connective tissue cell, x 400. 

parts of a tissue or 
cell to different degrees. In a cell it is noticed that the inner- 
most part is invariably colored the most intensely. In the 
case of the epithelial cell the nucleus will be stained a deep 
red by the carmine, while the outer part remains unaf- 
fected. Now if any young or rapidly 
growing epithelial surface be examined, 
as the layer of epithelium over a papilla 
of the tongue, those cells nearest the 
blood-vessels will be seen to take the 
carmine staining completely. They are 
composed of nucleus matter alone ; from 
this matter must come all the future 
parts of the cell. No matter how high 
fig. 14. Fuiiy developed or complex the tissue, it must proceed 

cell. a, formed material; . . . . 

b, nucleus; C| nucleolus. from this first living germinal matter, 
the bioplasm of Beale. If the cells be examined a little 
further from our nutrient vessel a material will be seen sur- 




34 



THE STUDENTS MANUAL OF HISTOLOGY. 



rounding the nucleus, which does uuc take carmine staining. 
This was once living nucleus matter but now from coming in 
contact with air or fluids death occurs upon its surface and 
the nucleus or germinal matter becomes changed to lifeless 
formed material. Still farther away on the surface of the 
papilla the nucleus has nearly disappeared. It is now 
so far removed from its supply of pabulum that it has become 
gradually changed. Nutritious material then is deposited 
from the blood, first, in the centre of the living part of each 
— cell, and while the inner part of each 

f^ __)X cell, the nucleus, is being constantly 

replenished, its outer part is as con- 
stantly passing into lifeless formed 
material. All matter must be nucleus 
matter before it can become formed 
material. Only nucleus matter can be 
said to live. It lives, because it is 
capable of converting material unlike 
itself into material like itself. The 
nuclei of muscle convert common pa- 
bulum into muscle nuclei which is 
thence converted into muscle formed 
material. The nuclei of nerve cells are 
capable of taking some of the same 
pabulum and converting it into nerve 
and thence into nerve formed 




FIG. 15. Illustrating diminish 
ing nuclei in cells as they approach nuclei 



the surface, a, cells near blood- 
vessels ; b ; ceiis remote from blood- material. Thus, man, a federation of 

vessels. 

these cells is capable of converting his 
food into materials like his own body, hair, nails, 
skin, etc., while the dog by eating of the same food 
will convert it into its own peculiar tissues. The youngest, 
most recently deposited matter of a tissue is found in its 
nuclei, the oldest in its formed material. There is a law 
in the body by which the amount of pabulum supplied to the 
nuclei by the blood, just equals the wear and waste of the cells. 



THE STUDENTS MANUAL OF HISTOLOGY. 35 

But if from any cause the part be irritated, be spurred to in- 
creased action, then an extra amount of blood flows to the 
part, an extra amount of pabulum is furnished to the germinal 
matter, causing it to increase rapidly. Now from two to five 
nuclei are seen in one cell. If the process goes on the 
changes become so rapid that the germinal matter does not 
change into formed material, and there now appear a multi- 
tude of round, globular bodies, in cells, and on the surface of 
cells, familiarly known as pus. Doubtless some of these 
cells are the migrated white corpuscles of the blood, but 
the mass of them represent living germinal matter undergoing 
rapid changes and possessed of a low vitality. This germinal 
matter may come from any irritated cell. It must be borne in 
mind that the supply, and change of pabu- 
lum to the germinal matter, and from it 
to the formed material of the body, are 
constant and uninterrupted. From what 
has been said it must be evident that com- 
pared to human life, the life of any one 

FIG. .6. Pus in epithelial cel [ } s yery short . 
cells found in urine, x 250. ■> 

When we consider the immense numbers removed daily 
from the surface of the body by the friction of clothing — 
laying aside the work of the sponge and towel — some idea can 
be gained how active must be the changes going on just be- 
neath the surface. Add to this the number rubbed off by 
every act of moving the tongue, in speaking, drinking, and 
eating, and we commence to understand how most of the cells 
are destined to an early death. This great loss is replaced 
by the formation of new cells and by the division of those 
already formed, — the nucleus dividing first, then the whole 
cell becoming separated into two by constriction. In 
order to understand the most complex we study the most 
simple. That we may the better understand the highest, 
we watch the lowest, for they all receive new material and 




7,6 THE STUDENTS' MANUAL OF HISTOLOGY. 

transform it into the constituents of their own bodies. They 
live, they grow, they reproduce their kind, they die. 

Our knowledge of the structure of cells and of their 
nuclei has been greatly increased by the labors of such men 
as Kleinenberg, Heitzman, Auerbach, Flemming, Klein and 
others. 

In No. 71, 1878, p. 315, and in No. 74, 1879, p. 125, 
of the Quarterly Journal of Microscopical Science, are ar- 
ticles by E. Klein, giving personal observations on the 
structure of cells and nuclei. The first article opens with a 
resume of the work of several observers. From this we 
learn that Frommann described a network of fibrils in the 
nuclei of many kinds of cells as early as 1867. 

In 1873, Heitzmann asserted that the substance of 

various cells, amoebae, blood-corpuscles, cartilage cells, bone 

cells, epithelial cells, etc., contains a 

t network of minute fibrils, into which 
pass fibrils radiating from the interior 
of the nuclei of those cells. 
To demonstrate this structure Klein 
places the tissue into a 5 per cent, so- 
lution of chromate of ammonia in a 
fig. 17. Epithelial ceii. closed vessel. It is kept here for about 

a, intracellular network ; b, , T , • ., i j • 

intranuclear network. 24 hours. It is then washed in water 

{ em ' for about half an hour, when it is 
placed in a dilute solution of picro-carmine, where it is left 
till it assumes a deep pinkish-yellow tint. 

Examined in glycerine the nuclei show a beautiful net- 
work of fibrils, "Intranuclear network." The nucleus is 
surrounded by a membrane which is in connection with the 
fibrils of the nucleus. 

The fibrils vary in the different nuclei. They may be 
fine, delicate and smooth, or coarse, of irregular outline and 
convoluted. Klein regards the "granules," or minute bright 
spots seen in nuclei, as representing the fibrils of the net- 



THE STUDENTS MANUAL OF HISTOLOGY. 37 

work seen in optical transverse section or at the point of 
anastomosis. Some fibrils, however, are possessed of irre- 
gular thickenings. He believes the so-called " nucleoli " are 
accumulations or local thickenings of the fibres of the in- 
tranuclear network. In many cells there exists a delicate 
fibrillar network in the cell substance — in the " formed 
material" of Beale. "Intracellular network." There is a 
direct, anatomical continuity of the fibrils of the intracellular 
network with those of the intranuclear network. In the 
meshes of this fibrillar network is a homogeneous " inter- 
fibrillar substance." 




CHAPTER III. 



Blood. 



BLOOD may be described as a tissue, the discs forming the 
essential element, the cells ; while the plasma represents 
the matrix in a liquid condition. If the matrix of bone could 
be liquefied so that the bone cells could freely move about, it 
could be well compared to blood as a tissue. Or if some re- 
agent could be applied to completely solidify the plasma, we 
should have a tissue not very unlike cartilage. 

As early as 1661 Malpighi discovered little particles in 
the blood of the ljedgehog, which he thought were little par- 
ticles of fat, but these were really the corpuscles of the blood. 
Only a few years later Leuwenhoek described quite minutely 
the corpuscles, which he had discovered in human blood, al- 
though the very best lenses at his disposal were made by him- 
self and did not magnify over 160 diameters. To him is given 
the honor of first discovering the corpuscles of the blood. It 
was not until a century later that another kind of corpuscles 
was discovered by Hewson, known as the white or colorless 
corpuscles, white globules, or the " leucocytes of Robin." 
Beside the liquid plasma, blood consists of, — 

First, red corpuscles. 

Second, white corpuscles. 

Third, accidental or temporary ingredients. 

38 '* ■ 



THE STUDENTS MANUAL OF HISTOLOGY. 39 



The corpuscles and plasma bear the following relations to 
each other. 

BY VOLUME. BY WEIGHT. SPECIFIC GRAVITY. 

Plasma, 60 per ct. 55 per ct. 1030 ) 

Corpuscles, 40 per ct. 45 per ct. 1088 j IO " 

The blood is distributed through the body of man in the 
following proportions : 

One-fourth in the heart, lungs, large arteries and veins. 
u u tl u liver> 

" " " " skeletal muscles. 
" " " " other organs. 

In the organs of the rabbit Ranke found the blood dis- 
tributed as follows : 









PER CENT. OF 
TOTAL BLOOD. 


[n 


the 


spleen, - - - 


• 2 3 


<< 


" 


brain and spinal 


cord, 1.24 


u 


tt 


kidneys, - - 


- - 1-63 


n. 


a 


skin, - - - 


2.10 


a 


a 


intestines, - - 


- - 6.30 


a 


a 


bones, etc., 


- - 8.24 


it 


i 


heart, lungs and 


great 






blood vessels, 


- - 22.76 


it 


a 


skeletal muscles, 


- 29.22 


<< 


it 


liver, - - - 


- - -'9-3° 



The total quantity of blood in the human body is esti- 
mated by different writers at from -J to -fa of the body weight. 



n the rabbit, 


/ s of body weight. 


" «■ dog, 




" " cat, 


A .. „ 


<• « frog, 


h " " 



40 THE STUDENTS MANUAL OF HISTOLOGY. 



THE RED CORPUSCLE. 

As seen in a single layer under the microscope the red 
corpuscles are of a yellowish-green tint, and it is only when 
seen in masses, that they present a reddish color. These red 
corpuscles are found in the blood of all the vertebrates, even 
in the lowest form, the amphioxus. 

THEIR ORIGIN AND DEATH. 

They are present in the blood of the embryo when the 
foetus is little more than -^ inch in length. At this time they 
are much larger than those found in the adult, varying in size 
from -g-J-jj- to 16 1 00 of an inch in transverse diameter. In shape 
they are circular, oval, or globular. Nearly all have a nucleus 
readily seen without the aid of reagents. 

What is the origin of these primary red corpuscles of the 
embryo ? 

Early in the history of the embryo the rudimentary heart 
consists of a mass of epithelial cells, and radiating from it are 
two or more tracts — generally one on each side — which, by 
their subdivision, form the vascular area. 

These cells are nucleated and vary in shape according to 
the pressure to which they have been subjected. In size they 
agree with the early red corpuscles described above. 

At a certain time some of these nucleated cells in the in- 
terior of the mass composing the rudimentary heart, become 
loosened from their fellows. The exact time of this occur- 
rence and its cause are not known. There are certain normal 
functions of the body performed in a regular way, the cause or 
causes of the regularity remaining in obscurity. We only 
know that these particular cells are separated from the rest to 
serve a special purpose as carriers of oxygen. 

The remaining cells become transformed into the tissue 
composing the walls of the vessel, which, by twisting upon it- 
self, finally becomes the heart. There is reason to believe that 



THE STUDENTS MANUAL OF HISTOLOGY. 41 

throughout the vascular area, cells in the interior of the blood- 
tracts become loosened from their fellows, while the remaining 
ones are metamorphosed into the walls of the vessels. These 
loosened cells may be either slightly or quite deeply colored. 
It would seem that the haemoglobin is deposited as small 
granules in different parts of the cells, to become evenly dis- 
seminated afterwards. 

At this time there are large, circular, oval, nucleated red 
blood-corpuscles, identical with those seen as late as the 
middle period of uterine life. They increase greatly by cell 
division, at least until the embryo reaches a certain age, after 
which their multiplication may be due to other causes. 






FIG. 18. Red blood-corpuscles of the human embryo, undergoing cell-division. 

(From Kirke.) 

The development of the red corpuscles in the adult is, 
and must be, different from their embryonic origin. The basis 
upon which this assertion rests must be stated, for it might be 
said that the corpuscles in the adult are either the identical 
ones found in the embryo, or that they are formed from these 
by cell division. 

The first statement cannot be true, for there is every 
reason to believe that the red blood-corpuscle is exceedingly 
short-lived, (see Foster's Physiology, 3d edition, p. 35.) The 
number of corpuscles in the blood varies greatly at different 
times, as is proved by counting them. Again, after hemoi- 



42 



THE STUDENTS MANUAL OF HISTOLOGY. 



rhage or disease, the normal amount may be regained in a very 
short time. If the urinary and bile pigments are derived from 
the haemoglobin, the number of red corpuscles destroyed must 
be very great. The second assertion cannot be true, for the 
corpuscles very seldom, if ever, increase by cell division in the 
adult {Ibid., p. 36.) 

' They must, therefore,,. have an, origin entirely distinct 
from that of the embryonic cells. 

The following serves to strengthen an old theory and 
answer some objections to it. 

If we take the pulp of the spleen and examine it carefully, 
there may be seen large circular cells, colored with haemo- 
globin. These cells are, perhaps, the 
protoplasmic cells of Kolliker. Some 
of them contain in their interior, the 
remains of from one to ten red cor- 
puscles. The reason why these very 
large cells are not found in the circu- 
lation, is probably because they are too 
large to enter the venous capillaries 
(see histology of the spleen.) 
Their large size is attained by appro- 
priating to themselves, through their 
amoeboid movements, the remains of 
one or more red corpuscles ; this oper- 
ation must take place in the spleen 
pulp outside of the vessels. Their size 
will prevent them from entering the first 
fig . 9 . Biood ceils from venous capillaries, until they have un- 
spieen pu'p^^ & Brown -, dergone cell division. This division 
may be due to the same cause that 
keeps the amoeba about an average size, viz.: the attraction of 
its constituent particles for each other not being equal to the 
external pressure after they attain a certain growth. As a re- 
sult of cell division, spherical, nucleated, colored corpuscles 




THE STUDENTS MANUAL OF HISTOLOGY. 43. 



would be produced, sufficiently reduced in size to enter the 
circulation ; and we have proof positive that they do enter as 
suggested above. Special precautions must be taken to de- 
monstrate the presence of these corpuscles in the circulating^ 
blood, and Schmidt believes them to be always present in nor- 
mal blood, in limited numbers. They are also seen in the 
medulla of bone. They have the appearance of white blood- 
corpuscles, colored with the haemoglobin of the red. 

When lymph, taken from the thoracic duct or any other 
lymph vessel in the system, is examined immediately, it is 
found to be colorless, or nearly so ; but when allowed to clot, 
it assumes a decided pinkish tinge, which, by microscopical 
examination, is found to be caused by the presence of red 
blood-corpuscles. The red corpuscles appearing so constantly 
after the withdrawal of the lymph from the body, could hardly 
have an accidental origin. (Dalton's Physiology, 6th ed., 
p. 368.) 

Recklinghausen saw the white cells of frog's blood 
develop into red corpuscles, even when out of the body. 
(Arch, fiir Mic. Anat., 1866, p. 137.) Were there not such a 
difference between them in structure and form, these facts 
would lead to the conclusion that the white corpuscles give 
origin to the red. Kolliker, Neumann, and Schmidt are of 
the opinion that the nucleus disappears from the white cells, 
while Huxley holds that the red corpuscles represent the bare 
nucleus of the former. Beale has taught us, that as the cell 
grows in age its nucleus diminishes in size. His method of 
staining certainly supports his statements. (Beale, Mic. in 
Med., 4th ed., pp. 232 and 259.) If the haemoglobin is not 
deposited in the white corpuscles until they have reached a 
certain age, they will be entirely without a nucleus. If, as 
claimed by Bottcher and verified at this laboratory (see Quar. 
Mic. Journal, October, 1878, p. 46), the red corpuscle has a 
nucleus, the haemoglobin must have been deposited prior to 
the time just given. 



44 THE STUDENTS MANUAL OF HISTOLOGY. 



This time may be associated with the period when the 
white cell ceases its active amoeboid movements, becoming 
passive, a condition which would occur most naturally when it 
was old and its nucleus small. The appearance obtained from 
following the methods of Bottcher is said to be due to the 
coagulating effect of the corrosive sublimate on the albumen 
of the red corpuscle. If this be true, it seems strange that the 
coagulating agent does not serve all red corpuscles alike and 
give a nucleus to each one. 

This bleaching, hardening and staining method of 
Bottcher proves the existence of three classes of red cor- 
puscles. 

The red corpuscles (very few in number) having a nu- 
cleus and nucleolus, are recently derived from young white 
corpuscles. Those having a nucleus only, are either from 
older white corpuscles or are the older forms of the red ones 
possessing a nucleus and nucleolus ; while those consisting of 
a homogeneous mass are either directly grown from the older 
white corpuscles, or are the oldest forms of those composing 
the first or second class. 

The results of Beale's investigations lead to no other 
conclusion, and the recent researches on the structure of the 
nucleus by Aurbach, Hertwig, Priestley and Klein, do not, in 
the least, invalidate these statements. 

Although there may be a difference in the structure of 
the red and white corpuscles, it is only such a difference as 
the growth of cells renders necessary. 

Some reason must be given for the change in shape from 
a spherical body to a biconcave disc. 

Haemoglobin possesses a great avidity for oxygen, it also 
retains this property when united with the white corpuscles, 
and under proper conditions, will combine with this gas even 
in excess. 

Will this excess of oxygen have any effect on the shape of 
tfie corpuscle ? t 



THE STUDENTS MANUAL OF HISTOLOGY. 45 

Using a carbonic acid gas apparatus, of the kind de- 
scribed in the Hand-Book for the Phys. Lab'y, by Burdon-San- 
derson, and examining the blood in a suitable chamber, the 
effects of the gas on the red corpuscles can be studied. 

It is not to be expected that the carbonic acid will unite 
with the red corpuscles, but the intention is to displace the 
excess of oxygen so far as possible, and thus reduce the red 
corpuscles nearer to the condition of the white. 

Experiments lead to the conclusion that one of the changes 
resulting from this displacement of the excess of oxygen, is to 
render the biconcave red corpuscles more globular. The alter- 
ation is not a complete one. The red corpuscle does not be- 
come as spherical as the white, but such a complete change 
might be confidently expected if all the excess of oxygen could 
be removed. The change in form, however, is sufficient to 
give rise to the belief that oxygen is the active agent in caus- 
ing the biconcave shape. 

In speaking of the difference in color between arterial 
and venous blood, Foster says (Foster's Physiology, 3d edition, 
page- 354, 1880) : "There may be other changes. * * * 
When a corpuscle swells, its refractive power is diminished. 
* * * Anything, therefore, which swells the corpuscles, 
tends to darken blood. *...** Carbonic acid has ap- 
parently some influence in swelling the corpuscles." And it 
might be added, it swells them because it displaces the excess 
of oxygen as described above. There is no such excess of 
oxygen in the white corpuscles, because they have no haemo- 
globin to draw oxygen to them. Dissolve out the haemoglobin or 
remove the excess of oxygen from the red corpuscles, and they 
will not be unlike the white in shape. Hence, all that is 
necessary to change a white to a red corpuscle is to dissemi- 
nate haemoglobin through the substance of the latter ; 
this will attract an excess of oxygen, and a change in shape 
will result. 



46 THE students' manual of histology. 

If the corpuscles have such a short existence, the question 
naturally arises : Where and how do they die ? 

The serum of fresh blood contains no dissolved haemo- 
globin, so that if any red corpuscles are destroyed in the cir- 
culation, either the number must be very small, or else the 
haemoglobin must be speedily transformed into some other 
body. 

Experiments made to show that the liver is a place of 
destruction for the red cells have given contradictory results. 
However, " a careful examination of the figures leads to the 
■conclusion that the red globules are rather destroyed than 
formed in the liver." {Physiology, Kiiss, 2d edition, page 124, 

1875-) 

An account of the histology of the spleen will throw light 
upon the matter under consideration. (See histology 
of the spleen.) 

Following the divisions of the splenic artery, it it seen to 
divide again and again, until finally the branches diminish to 
the size of capillaries. These soon become indistinct. Cell 
demarcations may still be recognized, but these also soon dis- 
appear, and there is now a minute blood current without definite 
walls. " As the failing branch of a drying brook wanders at 
last between the pepples of its bed, slender and scanty, so is it 
with these finest blood-currents." 

The blood enters the splenic artery and flows undisturbed 
through its branches to the very finest capillaries. The walls 
that separate it from the soft tissue now disappear, and it has 
to pass through a quantity of splenic tissue, with nothing to 
keep it from immediate contact with that tissue. 

Having no walls to confine it, it flows now this side and 
then the other side of the "pebbles" (lymphoid cells) of its 
bed. One portion of the red elements of the blood passes 
through this tissue into the primordial venous capillaries, and 
finally reaches the general circulation through the veins. 



THE STUDENTS MANUAL OF HISTOLOGY. 47 

Another portion, however, meets a mechanical death by stick- 
ing fast to the splenic tissue. 

The study of blood teaches that for the colored elements 
movement is life and rest is death. (Frey's Comp. of Histology, 
1876, p. 121.) 

The red corpuscles, being thus brought to rest, find their 
grave. But the younger corpuscles do not allow the older 
ones to remain quiet ; for, with an amoeboid motion, the white 
cells envelop the dead bodies of the red and greedily appro- 
priate them to their own use. In this way, the large white 
corpuscles mentioned above originate. 

If the spleen becomes enlarged, what will be the probable 
result ? The larger it becomes, the more tissue there will be 
through which the red elements must pass, the more fine 
blood-currents without walls, therefore the greater the destruc- 
tion of the red corpuscles. On the other hand, the number of 
the white cells will be correspondingly increased ; for the 
spleen must be considered as a birth-place of the white cor- 
puscles. (Foster's Physiology, 3d ed., p. 38.) 

The equilibrium will thus be destroyed and there will fol- 
low a great destruction of the red and a great increase in the 
number of the white corpuscles ; the extent of which will de- 
. pend upon the size of the spleen. 

Extirpation of the spleen does not always cause the result 
anticipated, and it is asserted that the number of white cor- 
puscles is not materially changed, neither does hypertrophy of 
the lymphatics always follow. In answer to this it may be 
said that extirpation of one kidney does not always lead to 
any material change in the amount of urine, neither does a 
microscopical examination of the remaining kidney, after a 
time, show any increase in size of either the tubuli or glom- 
eruli. (Flint's Physiology, Vol. III., 1876, p. 404.) 

The spleen is classed with the adenoid tissues. (Frey, 
Kiiss, &c.) Extirpate the spleen, and, as in the case of the 
kidney, the remaining adenoid tissues will cany on the work. 



48 



THE STUDENTS MANUAL OF HISTOLOGY. 



When the spleen is removed an abnormal condition is in- 
duced and it would be difficult to assert where the red cor- 
puscle meets its death. 

Therefore, the origin of the very first red corpuscle is 
from nucleated cells in the vascular area ; a little later in em- 
bryonic life, from cell division. Their origin in the adult is 
from the leucocytes ; the latter, becoming impregnated with 
haemoglobin, owing to the action of oxygen change to bicon- 
cave discs ; the nucleus of the white cells becoming gradually 
changed into the formed material of the red. Their death is 
owing to a mechanical cause in the spleen, and probably oc- 
curs, to some extent, in the liver also. 

THEIR SHAPE. 

In shape they are circular, flattened, biconcave discs with 
rounded borders. When seen on the side the centre appears 
either light or dark, depending on the focus. Acting as a 
biconcave lens, when the objective is slightly within the focus, 
the centre appears light, when without the focus, dark. This 
led the older observers co regard this centre as a nucleus. 
They were "optically deluded." (See Fig. 21.) Their shape is 

B 





FIG. 20. A. Human blood in rouleaux, a, white corpuscles, x 400. 
B. Human red blood-corpuscles, a, seen on edge, b, white corpuscle, x 1000. 

readily altered by the aid of reagents and is spontaneous y 
changed by their removal from the circulating fluid unless 
especial precautions be taken for their preservation. The red 
corpuscles of all the mammalia are of this shape with one ex- 
ception, the camelidae, in which they are oval. 



— 



THE STUDENTS MANUAL OF HISTOLOGY. 49 

THEIR NUMBER, VOLUME AND SUPERFICIES. 

They exist in great numbers. It has been estimated that 
in man there are five millions of them in a cubic millimetre of 
blood. Welcker estimates the mean volume of a red corpuscle 
to be .000,000,072,214 of a cubic-millimetre, and the super- 
ficies .000,128 of a square millimetre. Taking the number of 
corpuscles in a cu. mm. at five million, we should have in one 
cubic millimetre of blood 640 square millimetres of surface. 
In an ordinary man of 140 pounds weight, we will say there 
are 12 pounds of blood, a low estimate according to many 
authorities. If the amount of superficies of the red corpuscles 
be computed for the whole 12 pounds of blood, it will give us in 
round numbers 38,000 square feet. Although the circulation is 
complete in a less time, yet a quantity of blood, equal to the 
whole amount in the body, passes through the lungs in not far 
from forty-five seconds of time. In forty-five seconds the 
heart will beat about fifty times. Then one beat of the heart 
must send into the lungs 760 square feet of surface to be oxi- 
dized. In the normal condition then there is this amount of 
surface of red corpuscles in the lungs at any one time, exposed 
to atmospheric action. We are better prepared now to under- 
stand why blood is capable of absorbing 13 times as much 
oxygen as the same amount of water. The red corpuscles 
contain less water than the serum. In 100 parts of wet cor- 
puscles there are of water 56.5 parts, and of solids 43.5 parts. 
Haemoglobin constitutes over 90 per cent, of the dried organic 
matter of the human red corpuscles. 

THEIR STRUCTURE. 

The structure of these bodies is of great interest. They 
are so susceptible to the action of reagents, and are so liable 
to undergo various changes when removed from the circulating 
fluid that their study is most difficult. Two questions 
present themselves : Has the mammalian red corpuscle an 
investing membrane ? Has it a nucleus ? In reply to the first 



50 THE STUDENTS MANUAL OF HISTOLOGY. 

we say : the effect of mechanical agents, the fact that at no 
time is anything seen at all resembling a torn or empty mem- 
brane, and the effect of heat ; the study of these makes one 
believe that this body is without a membrane. Believing the 
red corpuscle of newt's blood to possess an envelope, and 
knowing that the mammalian corpuscle acts toward reagents 
like it, Rutherford, from analogy, infers the existence of a 
membrane in the latter. Hensen and others are of like 
opinion. The majority of histologists, however, fail to find 
satisfactory evidence of the existence of such a membrane. It 
appears that the outer part of the corpuscle is more dense than 
the inner. It conforms more nearly to our ideas of the 
•' formed " part of a cell. 

Has the red corpuscle a nucleus ? The great majority of 
histologists are ready to answer positively, No. But in the 
Arch, fur Mic. Anat., Bd. 4, Professor Bottcher gives the 
results of some researches on this subject, confirming him in 
the belief first advocated by Rollet. 

He uses a saturated solution of corrosive sublimate in 96 
per cent, alcohol, and into fifty volumes of this solution, one 
of blood is to be rapidly diffused. 

By this means the coloring matter of the corpuscle is 
taken out — bleached — and thus the internal structure brought 
more clearly to view. This solution preserves the corpuscles 
as well. 

By agitating the mixture now and then the process is 
hastened, and in about twenty-four hours the corpuscles arel 
allowed to subside, the superincumbent fluid poured off and- 
pure alcohol added in like amount. 

In another twenty-four hours this is poured off and 
distilled water added. The corpuscles are now thoroughly 
washed, and are not acted upon by the water. 

Professor Bottcher employs eosin, hematoxylin, picric 
acid and carmine as staining agents, but prefers the first. 

He finds three classes of corpuscles : 



1 



THE STUDENTS MANUAL OF HISTOLOGY, 



51 



First. Homogeneous and shiny throughout. 

Second. Added to this a granular mass in the center 
which stains readily. 

Third. Besides the cortical layer and protoplasm, 
closed in the latter is a marked nucleus and a nucleolus. 

Some blood was exam 



m- 



ined from a man acci- 
dentally poisoned with an 
alcoholic solution of corro- 
sive sublimate with the 
/a? result of finding nuclei in 

/®j B /Si) tne corpuscles. 

k~s ^W/ a s soon as the public 

announcement of Professor 
Bottcher's discovery came 
to our notice, his method 
was carefully followed at 
this laboratory, the blood 
from several mammalia be- 
ing examined. In nearly 
every case the first and 
second classes of corpuscles were found. It was quite rare to find 
those cells showing a nucleolus also. Only a few were found 
in all our work that appeared to be changed by the action of 
the reagent used. This nucleus has been demonstrated to 
students in the laboratory and to different members of our 
faculty. Various methods have been successfully used by 
different workers to show this nucleus. In the hands of others 
these same methods fail to produce the desired results. The 
real question at issue is this : Is the body found inside the 
mammalian red corpuscle, both with and without reagents, a 
nucleus? We are told that there is a structure characteristic 
of nucleus matter, an intra-nuclear fibrillar network ; but one 
is unable many times to see this network in that part of the 
cell admitted bv all to be the nucleus ; and as a fact all 



FIG. 21. The red blood corpuscles of man, treated 
by Bcettcher's method. A, homogeneous throughout. 
B, showing nucleus. C, showing nucleus and nu- 
cleolus. (Selected from Bcettcher's article, Oct., 
1877, Quarterly Journal of Mic'l Science.) 



52 THE STUDENTS MANUAL OF HISTOLOGY. 

nuclei do not seem to be possessed with it. Without any such 
distinctive structure as a guide how can we decide whether 
this is a nucleus or not ? No other way appears open to us 
but a course of reasoning such as is advanced on page 44 on 
the origin of this body. The question must be regarded as 
unsettled, for while our own believe makes us declare in favor 
of the presence of a nucleus we would remind the student that 
such is not the generally accepted view, which is, that the red 
corpuscle is a homogeneous mass without membrane or 
nucleus. 

THEIR SIZE AND MEDICO-LEGAL VALUE. 

The size of these corpuscles varies not only in the same 
individual at different times, but also in the same drop of 
blood examined at any one time. The size usually given is 
from the -g-^- to -3^-0 of an inch. The following is a list of 
measurements of the red corpuscles of different animals as 
given by Gulliver : 

D °g> mkv Horse, ^gVr 

Cat > 44V4 Goat > 

H °g> T2V0- shee P> 

Ox, 4-2VT Red squirrel, 

Brown rat, -g-gVr Black squirrel, 3 

Mouse, 38V4 Gra Y squirrel, ^Vo 

(For full table see Sydenham edition of Hewson's works, p, 237.) 

What is the value of these corpuscles in criminal cases ? 

That is, by a microscopical examination of a blood stain 
or clot, either fresh or otherwise, can we distinguish human 
blood from that of the inferior animals ? This must be con- 
sidered a very easy matter in some cases. Take, for instance, 
the red corpuscles of all the birds, reptiles, amphibia and 
fishes, here they are large oval bodies with a large round or 
oval nucleus. The only known exception to this is in the case 
of the family of lampreys. In these fishes the corpuscles are 
circular, yet they have a nucleus very easily seen without the 



63*66" 



4 
1 



THE STUDENTS MANUAL OF HISTOLOGY. 53 



use of reagents, hence are readily distinguished. If, then, the 
question arises, " Is this human blood ? " and upon examina- 
tion corpuscles are found of oval shape, the answer, No, can 
positively be given. If, however, the corpuscles are found 
circular in shape, and no visible nucleus without reagents, 

B 
A 







FIG. 22. A. a, red corpuscles viewed within the focus ; b, the sa.ne without the 
focus, x 750. B, Frog's blood, x 400. 

then an entirely different problem is involved, for with one 
exception (cameleidce) the corpuscles of the blood of all the 
mammalia are of this shape. Here the question must be 
decided by measurement. First of all there must be fixed, 
if possible, a standard size for the human red corpuscle, for 
the size of the corpuscles of many of the inferior animals 
is so nearly like that of man that our figures in each case 
must give a fixed average size. Has the red corpuscle of man 
a fixed size ? Most assuredly No, for it will be a difficult matter 
even to get an average size. In examining a drop of blood 
with high powers, one very frequently finds a few minute 
colored corpuscles below the j-gVo °f an inch. No account 
will be taken of these in arriving at the size of the red cor- 
puscle, they are easily excluded, and are few in number. The 
following are the average measurements of the red corpuscles 
of man : 

Gulliver, iMn) °f an inch. 

Flint, ^Vtt 

Dalton, jnVf to ^ " 

Richardson, TS V^ " 



54 



THE STUDENTS MANUAL OF HISTOLOGY. 



Woodward, 30V2" °^ an inch. 

Fre ^ 2T40 t0 innnr " 

Welcker, ^^ 

Our own observations give B J 61 as the mean. Thus it 
cannot be said that there is any settled average size, each 
investigator having an average of his own. While some are 
found as small as the -g-^Vr °f an inch, others are as large 
as the ytot °f an i ncn - Schmidt says, however, that over 
90 per cent, of the corpuscles found in a single specimen 
are of the same dimensions. This much can be said, that 
after measuring a large number of corpuscles, if their 
average diameter is either 3 g 1 Q0 or 3 * 0Q of an inch, or any 
fractional part between these two (-3-5V0 an d 3 20 ) the blood 
may be that of man. While a number of the lower animals 
have blood corpuscles within these limits, (monkeys, ba- 
boons, etc., beaver, guinea-pig, porcupine, etc.), yet only the 
blood from certain of the inferior animals will be liable to 
enter a medico-legal contest. 

Can dog's blood be told from human ? Mr. Woodward 
must have settled this point conclusively. " The average of 
all the measurements of human blood I have made, is rather 
larger than the average of all the measurements of dog's 
blood. But it is also true that it is not rare to find speci- 
mens of dog's blood in which the corpuscles range so large 
that their average size is larger than that of many samples 
of human blood." The mean average of corpuscles in 22 
drops of human blood (1766 corpuscles) ranged from .000,- 
309 to .000,343 of an English inch. Nearly the same num- 
ber of corpuscles of dog's blood gave .000,296 to .000,340 
of an inch. (Monthly Mic'l Jour., 1876, p. 132.) 

Can the blood of the cat, hog, horse, sheep and ox be 
told from human ? 

Although the corpuscles of the blood of the dog and 
of man are so nearly identical that even in freshly prepared 



THE STUDENTS MANUAL OF HISTOLOGY 



55 






specimens they cannot be distinguished positively from each 
other ; yet the corpuscles of the blood of the animals just 
mentioned, — cat, hog, etc., — are so much smaller than human 
blood-corpuscles that a positive distinction is possible, not 
only in freshly prepared specimens, but also when they are 
found in stains, clots, etc. 

If, then, the question is asked, — Is this the blood of 
man as distinguished from the blood of all other animals ? 
We shall be forced to reply, it is impossible to tell. If, 
however, the question is to decide between the blood of 
man and one of the inferior animals many times a most 
positive answer can be given. Between the blood of man 
and his most constant companion, the dog, there seems to 
be no difference, while it is possible to tell the difference 
between the blood of man and the blood of the sheep, hog 
horse and ox. 

To examine the stain, some of the dried blood is scraped 
from the surface to which it is attached, and the dried clot 
placed on a slide, over this is placed a thin glass cover, and 
a drop of the .75 per cent, salt solution being placed at its 
edge runs under the cover and moistens the specimen. The 
specimen is then examined with the highest power at com- 
mand. If particles of clot are so deeply colored that the 
corpuscles are indistinct, their coloring matter may be washed 
out by a current of the salt solution. This current is easily 
established by placing a piece of blotting paper just oppo- 
site where the solution is applied. If now the corpuscles 
are too pale they can be colored. Those corpuscles most 
perfect in shape should be chosen, a large number of them 
accurately measured and their average diameter ascertained. 

BLOOD CRYSTALS. 

Blood crystals may readily be obtained from the rat as 
follows : a drop of blood is mixed with twice its volume of 
water and then allowed to evaporate slowly. Prismatic crystals 



56 



THE STUDENTS MANUAL OF HISTOLOGY. 



of haemoglobin will be seen. The blood of the guinea-pig crystal- 
lizes very easily giving the beautiful tetrahedral crystals seen in 



« 3 

O © 



5 

Q 




FIG. 23. Showing relative size of red blood-cor- 
puscles of different animals. 1, man. 2, whale. 3, ele- 
phant. 4, mouse. 5, horse. 6, musk deer. 7, humming 
bird. 8, pheasant. 9, pigeon. 10, snake. 1 1 . crocodile. 
12, triton. 13, proteus. ^Altered from Gulliver.) 



fig. 24. In the squirrel the 
crystals are hexagonal 
tables. The blood of most 
of the mammalia including 
man, yields generally pris- 
matic or rhomboidal 
crystals. To obtain haemin 
crystals, a drop of blood is 
placed in a watch crystal 
and about 20 times its bulk 
ofglacial acetic acid add- 
ed. The mixture is then 
warmed and as it evapor- 
ates the desired crystals 
will be formed ; or to a 
drop of dried human 
blood add a few crystals 
of common salt, cover 
with a thin film of glass 
and place a drop of glacial 
acetic acid to its edge 
and allow it to run under 
and come in contact with 
the blood. . The specimen 
is then carefully warmed 
and soon the reddish- 
brown haemin crystals ap- 
pear. 



METHODS OF EXAMINING. 

If a drop of blood be placed on the slide, covered at once 
with the thin glass and transferred to the microscope, the 



THE STUDENTS MANUAL OF HISTOLOGY. 



57 




vh 



v^ 



<> 






examination will be anything but satisfactory. The number of 
corpuscles in the field is so great and the number of layers so 
many that the specimen cannot be studied to advantage. 
Again, if mixtures are used to dilute the blood, unless prepared 
a with the greatest care, they will 

cause changes in the corpuscles. 
When but a comparatively short 
examination is required, the fol- 
lowing method has always been 
highly satisfactory to us and is 
constantly employed in this labor- 
atory. To procure the drop of 
blood, one of the fingers is con- 
gested by tying around its base a 
string or handkerchief. When 
well filled with blood a fine cam- 
bric needle is quickly thrust 
through the outer coats of the 
skin over the end of the congested 
organ. One surface of a glass 
slide is now gently breathed upon 
and a drop of blood, pressed from 
the puncture, is brought in contact 
with this slightly moistened sur- 
face. One surface of the cover glass is now breathed upon 
and immediately its edge is placed close to, just in contact with, 
the edge of the drop of blood. With the aid of a needle the 
cover is lowered away from the drop, — not over it, — until it 
touches the slide. The blood corpuscles will readily flow be- 
tween these moist glasses, by capillary attraction, until the 
surface beneath the cover glass is nearly or entirely covered. 

There is but one single layer of corpuscles and they show to 
the best possible advantage. For this method to be successful 
it should be carried out rapidly and the moisture should not be 



/• *' *m 



\/ 






% 



i 



IV 

V 



FIG. 24. A. Hsematin crystals, human 
B. Haemin crystals, human. 



58 THE students' manual of histology. 



in excess, lest the water cause some change ; it should be suf- 
ficient, however, to allow the corpuscles to flow readily under the 
cover. The amount of moisture to be impartedby the breath is 
soon learned after a trial or two. If desired, a layer of oil may be 
placed around the cover glass and thus prevent the drying of 
the specimen. 

Examined with a magnifying power of about 450 diame- 
ters one never fails in a specimen prepared as above to see 
most beautiful and perfect representations of the rouleaux, 
where a greater or less number of red corpuscles adhere to- 
gether by their flat sides. A few corpuscle will be seen in the 
field alone, the majority of these few have a different appear- 
ance from those in rouleaux. They are larger, globular, and 
more granular. They are the white blood corpuscles or leu- 
cocytes. If the cover-glass be touched lightly with a needle 
the red corpuscles will roll about readily and their rouleax will 
be destroyed, while the white ones do not roll about readily 
and appear as islands in the midst of a rapid stream. Another 
satisfactory method of obtaining a thin layer of blood is to 
draw the edge of a smooth glass slide over the fresh blood and 
then drawing this edge of the slide across the flat surface of 
another slide. The thin cover is at once applied and the speci- 
men examined. Reagents can be applied by simply touching 
a small drop to the edge of the cover glass. 
action of reagents. 

Water has the effect of changing the red globules to a 
spherical form. Many times the central depression of one 
side will disappear before it does on the other, giving them 
a peculiar cup-shaped form; finally the water dissolves out 
the coloring matter, the corpuscles become paler and paler 
until after a time they are totally disintegrated. Acetic acid 
brings about these changes with great rapidity. The alkalies 
are very active in dissolving their whole substance. A 1 p. c. 
solution of salt will cause the red corpuscles to assume the 
crenate or horse-chestnut form, in which their surface is 



THE STUDENT S MANUAL OF HISTOLOGY. 59 

covered with minute spinous projections. This same appear- 
ance is seen in corpuscles that have been exposed to the air a 
short time. This may be due to the loss of carbonic acid by 

a the plasma, the cor- 

v — \ B 

V v &k **\ puscles then loose car- 



\1J *W <^£ bonic acid themselves 

(2) Ky. f*k ffib anc * tn * s ls f°ll° we d by 



O^^ v^» .*. -v- a shrinking of part of 



stroma, probably 
1 J *^ #$} the net-work of fibrils. 

FIG. 25. A, red blood corpuscles after the action of (Klein.) EleCtHC dlS- 
water. B, the same after the action of salt solution. charges of the levden 

jar cause them to assume the crenate form, to finally swell 
up and become deprived of their color. Tannic acid, in a 
2 p. c. solution causes the haemoglobin to collect at the 
periphery in the form of one or more round masses. 

THE WHITE CORPUSCLE. 

Besides the red corpuscles there are seen other cellular 
bodies which are unlike the former in shape, size, structure 
and color. 

As seen under the microscope they are destitute of any 
color, hence they are called colorless corpuscles, or white cor- 
puscles. 

A In nearly every spe- 

cimen of blood some 
white corpuscles will 
be found smaller than 
the red, but the great 
majority are larger, 
not only in man, but 
in all the mammalia, 

FIG. 26. Pus. A, before, and B, after, the action of 
dilute acetic acid. while in Other animals, 

owing to the large size of the colored corpuscles, the white arc 
the smaller. They are about the same size in ail the verte- 





60 THE STUDENTS MANUAL OF HISTOLOGY. 

brates, and although varying in the same and different speci- 
mens, yet their diameter will not vary far from the 2 £ 00 of an 
inch. When dead, or in a quiescent state they are nearly 
spherical, but when living they are capable of altering their 
shape in a most remarkable manner, their substance projecting 
into prolongations which in turn are retracted into the body of 
the cell after the fashion of our amoeba (page 30.) The white 
corpuscles of the blood of the newt can be seen to undergo 
these amoeboid movements without any extra care on the 
part of the operator. In the case of those from human blood 
it will be necessary to have the specimen maintained at, as 
nearly as possible, the same temperature as that of the body, 
viz., 98.5 degrees F. 

The number of white corpuscles does not bear any con- 
stant relation to the number of the red. Before meals the 
number of white to red is about as 1 to 300. In a fasting con- 
dition the number may decrease until the ratio is as 1 to 
1000. In certain pathological conditions the number of white 
corpuscles is increased until they nearly, if not quite, equal 
the red. If fluids be taken freely with a meal the number of 
white corpuscles is greatly increased, while if a meal be taken 
without drink the number may remain the same or even be 
diminished. 

If a current be established through the specimen the red 
corpuscles can all be washed away and the white left alone in 
the field. They appear as highly transparent bodies, dotted 
with minute granules. In each globule there is one nucleus, 
capable of amoeboid movements independent of the body of 
the cell. Often two or three nuclei with nucleoli are present. 
Heitzman makes the white corpuscle composed of a minute 
net-work of fibrils, — the intra-cellular net-work — in the meshes 
of which there is an interstitial hyaline substance ; and the 
granular appearance is simply these minute fibrils seen in 
optical section. The nucleus also is composed of an intra- 



THE STUDENTS' MANUAL OF HISTOLOGY. 6 I 

nuclear fibrillar net-work which is directly connected with 
the intra-cellular. This appearance can be seen only under the 
most favorable- circumstances. 

The large granular corpuscles seen in human blood con- 
sist of a deposit of real granules in the meshes of this intra- 
nuclear net-work. These granules may be the broken- 
down remains of what once constituted the minute fibrils of 
the corpuscles. 

The white corpuscles are continually being removed or 
changed into other forms, for their number varies extremely 
under different circumstances and at different times. Whence 
the supply? 

We find the lymph constantly pouring into the blood vast 
numbers of them which appear for the most part after the lymph 
has traversed the lymphatic glands. In a section of a lymphatic 
gland are seen corpuscles identical with the white corpuscles 
of the blood. They are of different sizes and have dividing 
nuclei. Klein says that he has seen these corpuscles budding 
off" from the reticulum of the spleen. There origin then is 
chiefly from the lymph corpuscles of the lymphatic glands. 
Other sources may exist, as from the endothelial cells of serous 
membranes, and from almost any proliferating tissue. 

ACTION OF REAGENTS. 

Dilute acetic acid increases their transparency and renders 
the nuclei more perceptible. Its final effect is the same as 
that produced by water, viz.: their total disintegration. 

Alkaline solutions if strong enough dissolve them. 

A slight electric shock causes the living corpuscle to con- 
tract, while a strong shock has the same effect as the three 
reagents just given. 



CHAPTER IV. 



Epithelium and Hair. 

UNDER this head we include the crowded cells covering 
mucous membranes and the skin, also the cells lining 
secreting and allied glands. Epithelium may be divided into 
two classes according to the form of the cells, i. Columnar, 
in which the cells are long and narrow. 2. Pavement, in 
which the cells are flattened. As varieties of the first class 
we have cylindrical, ciliated, etc., and of the second class 
scaly, buccal, flattened, etc. 

Epithelium may be arranged in a single layer as on the villi 
of the intestine or in stratified layers as on the surface of the 
body. When stratified layers of epithelium occur it is almost 
invariably of the pavement kind, although this class appears 
as a single layer in many parts of the body. Cylindrical 
•epithelium rarely presents more than a single layer. 

If epithelial cells be separated from their natural connec- 
tions by the aid of the clean blade of a knife and placed with 
an indifferent fluid on a glass slide, covered, and examined 
with a high power, cells will be found isolated and favorable 
for study. They appear to be composed of a soft albuminous 
matter in which is a large number of "granules." Under most 
favorable conditions one is able to see what Hutzmann, 
Eimer, and Klien first taught, namely, that the body of the 
cell is composed of a minute intra-cellular net-work of fibrils, 
in the meshes of which is a hyaline substance. In the ordinary 

62 



THE STUDENTS' MANUAL OF HISTOLOGY. 63 

pavement variety'this fibrillar net-work is irregularly arranged, 
while in the columnar variety the intra-cellular fibrils have a 
longitudinal arrangement, parallel to the long axis of the cell. 

According to this view, the familiar dots or small granules 
are these intra-cellular fibrils seen in optical section. Some of 
these cells certainly appear to have a membrane; this may be 
the hardened part of the cell from evaporation, or more 
probably the dense exterior of its formed material. 

With the exception of those cells on the surface of the 
body, each cell has a nucleus surrounded by a membrane, and 
composed of an intra-nuclear fibrillar net-work. In its meshes 
we find an interstitial substance. The granules are due here 
to the same cause as those found in the body of the cell; some- 
times however they represent the broken-down remains of 
fibrils when they are true granules. Inside the nucleus is seen 
frequently a nucleolus, from which the nucleus is developed. 
A refractile body, seen in the nucleus at times and resembling 
a nucleolus, is found, upon closer examination, to be a part of 
the shrunken intra-nuclear net-work. The cells are held in 
close contact with each other by an albuminous substance 
termed "cement substance." In examining transverse sections 
of hardened specimens, this substance looks like a thin mem- 
brane separating the cells, but in the fresh specimens it is clear 
and viscid. Many of these cells are being constantly discon- 
nected from their bases by the acts of nature. The old cells 
are ever falling off spontaneously and as the result of the 
pressure and friction to which many surfaces of the body are 
subject. Some of them seem to be more enduring in their 
nature as those found in different parts of the eye. 

CILIATED EPITHELIUM. 

Certain of the columnar cells have fine hairs on their 
bases, called cilia. These cilia are but the prolongations of the 
fine protoplasmic filaments, — the intra-cellular fibrils — through 



64 



THE STUDENTS MANUAL OF HISTOLOGY 



the base of the cell. The regular vibrations of these cilia led 
the old observers to discuss electrical attraction and repulsion. 
Klein explains this motion as follows: 

He supposes that the "intra-cellular net-work contracts to 
one side in a horizontal diameter; each such contraction acts 
naturally on the lower ends of the cilia, which are pulled thereby 
to the same side, while the outer or freely projecting portions 
of the cilia are driven in the opposite direction. Each cilium 
represents a lever, the short arm of which is within the cell in 
connection with the intra-cellular net-work, the long arm being 

the freely projecting part 
and the fulcrum or fixed 
point lying in the mem- 
brane covering the free 
cell border. The next 
moment the contraction of 
the intra-cellular net-work 
ceases and the cilia move 
again in the opposite 
direction." 

METHODS OF EXAMINING. 

For samples of colum- 
nar epithelium remove a portion of the intestine of a recently 
killed rabbit or cat, and wash carefully the mucous membrane 
by flowing over it some of the salt solution. Then with the 
point of a scalpel transfer a small portion of the membrane to 
a glass slide and to it add a drop of staining fluid. Certain of 
the villi will be removed entire, but a few of the columnar cells 
will be seen floating free in the field. At fig. 28 are seen a few 
of these cells. An oval nucleus is present in each cell bounded 
by a distinct line. These cells terminate usually in a fine 
point, a few are bifid, while others terminate in a rounded ex- 
tremity. At the free border of the cell is a thickened margin 




B 



fg> 


<$!!$ 


w. 


m 








m 


m 


m 




$ty£ 


nfc- 


Intilii 




FIG. 27, A, Ciliated cell. B, Columnar cell. C, 
The columnar cell, B, changed into a goblet cell and 
filled with mucin, (after Klein and Smith.) 



in which fine vertical striae are seen. 



THE STUDENTS* MANUAL OF HISTOLOGY. 



65 




FIG. 28. Epithelium from intestine, 
goblet cells, x 400. 



If the animal be killed during digestion, globules of fat 
within the cells will be recognized by their strong refractive 
power. A few cells may be seen of peculiar chalice shape 
called " goblet cells." The part of the cell nearest its free 
border has swollen out owing to the conversion of its inter- 
stitial substance into mucin. The membrane at the base will 

finally rupture, and the mucous con- 
tents be poured out. The nucleus 
will be found toward the distal end 
of the cell. Haematoxylin stains the 
mucous contents of these cells a deep 
purple-blue. Pieces of the small 
intestine of the cat or rabbit may be 
hardened in a one per cent, solution 
of potassic bichromate or osmic 
acid. In a few days a portion of 
the mucous membrane may be re- 
moved and examined in the salt solution. All parts of the 
cell now show to better advantage. The fatty particles in the 
cells are colored black by the osmic acid, and the speci- 
mens can be permanently preserved in glycerine. If the free 
surfaces of the cells be turned toward us, they present a 
beautiful mosaic, caused by their collateral pressure during 
their growth. 

Impregnation with silver is to be especially recommended 
in studying the epithelia. For this purpose the specimen is 
immersed in the solution for a short time, perhaps the fraction- 
al part of a minute, when it is removed, washed in water 
and exposed to the light until it assumes a brownish color. 
The specimen is then examined in acidulated water or in 
dilute glycerine. This colors the cement substance, the cell 
itself not being affected, and the boundary lines become very 
distinct. The cells may be afterwards stained with carmine if 
desired. Very weak solutions of the silver (argentic nitrate) 



66 THE students' manual of histology. 

are employed, from .2 to .5 per cent, and in some cases even 
weaker solutions can be more advantageously used. 

CILIATED EPITHELIUM. 

This may be readily obtained by gently scraping the 
mucous membrane on the roof of a frog's mouth. If a large 
amount be desired, the frog may be killed and this entire mem- 
brane dissected off. For ordinary purposes sufficient epithe- 
lium will be brought away with the mucus by scraping the 
membrane in situ with the point of a clean scalpel. A drop of 
normal saline solution has been placed on the centre of a glass 
slide and on either side of it a hair, in order that the cover 
glass may not press upon the cilia and thus check their vibra- 
tions. The adherent mucus is now transferred from the knife 
to the salt solution. The preparation should be covered and 
examined at once with a power of at least 450 diameters. The 
cilia will be seen in active motion, driving any particles that 
come near them in one direction. If the cells are isolated or if only 
a few are in a group, the cilia will act like little paddles, 
causing the cells to whirl around and move about over the 
field. If there are no blood-corpuscles or granules to be 
driven about, particles of carmine may be added to the speci- 
men. This is best done by mixing a little granule of carmine 
with water and placing a drop to the edge of the cover glass. 
Diluted with water aniline red will tinge the cilia without 
causing their motion to cease. (Aniline red=Fuschin, 1 centi- 
gramme. Absolute Alcohol, 20 — 25 drops. Water, 15 cubic 
centimetres.) The action of cilia may be strikingly shown by 
examining the gills of a living oyster or of a clam. 

This variety of epithelium is found in the following places 
in the human body: Throughout the upper part of the nasal 
passages, nasal duct, posterior surface of soft palate, upper 
part of pharynx, larynx, trachea, bronchial tubes to near their 
termination, eustachian tube, tympanic cavity, internal surface 



THE STUDENT S MANUAL OF HISTOLOGY. 



67 



of eyelids, ventricles of brain, central canal of spinal cord, 
fallopian tube, body and, according to some authors, neck of 
r-terus, vascula efferentia, coni vasculosi, and canal of epidid- 
ymis, and upper half of vas deferens. 

ACTION OF REAGENTS. 

Electrical currents, heat, and any fluid currents all accel- 
erate the motion of the cilia. Carbonic acid first accelerates, 

then checks, and finally arrests 
their action. When the motion 
has just ceased slightly alkaline 
fluids will apparently call it to life 
again for a short time. 

To obtain squamous, or buccal 
epithelium move the tongue 
roughly over the gums and interior 
of the mouth, then place a large 
drop of the saliva on the slide. 
The air bubbles may be removed 
by passing a needle horizontally 
over the specimen skimming them off ; cover and examine. 




FIG. 29. Ciliated epithelium from 
uterus ^human). x 400. 




FIG. 30. Saliva, a, epithelial cells, b, salivary corpuscles, x 400. 

The cells are partly isolated, partly hanging together. Their 
large size, 1-450 to 1-750 of an inch, and their single small 



68 



THE STUDENTS MANUAL OF HISTOLOGY. 



nucleus are characteristic. A varying number of salivary cor- 
puscles is seen in every specimen. They are rather larger 
than the white blood-corpuscle and there is a peculiar Brownian 
movement of their enclosed granules. One is inclined to be- 
lieve, however, that these are exuded white blood-corpuscles 
swollen by the watery constituents of the saliva. In examin- 
ing the saliva one frequently finds remains of food, as fibres of 
meat, starch granules, etc. 

Pigmented pavement epithelium may be found covering 
the choroid, ciliary processes and posterior surfaces of the 
iris. Shreds of it may be removed with a scalpel and examined 
as usual. Here again the cells form a beautiful mosaic of a 
hexagonal form. 

The pigment granules may be so 
numerous as to entirely obscure the 
nucleus, while in other cells only a few 
of the melanotic molecules are embed- 
ded in the soft substance. The glandu- 
lar and allied varieties of epithelium 
will be studied in connection with the 
different organs. The surface of the body 
is covered everywhere with a stratified layer of epithelial cells. 
If the skin be scraped with a scalpel a fine dust is obtained, 
which, examined in fluid, is found to consist of irregular, 
broken epithelial cells without a nu- 
cleus. These layers of cells are best 
studied in a section of skin. (See or- 
gans of sense.) Closely allied to these 
cells are those found in human nails, 
which commence the third month of 
fcetal life as an elevacion of the skin of 
the distal phalanx. The nail substance 
is composed of epidermal cells very 
closely united, but easily separated by a 




FIG. 31. Pigment epitheliur 
(Choroid.) x 400. 




FIG. 32. Epithelium from the 
back of the hand. a, from sur- 
face, b, deeoer x 400. 



THE STUDENTS MANUAL OF HISTOLOGY. 



6 9 




FIG. 33. Epithelium from the nail x 400. 



number of chemical reagents. These cells are irregular in 
shape and enclose a round or lens-shaped nucleus. A 27 p. c. 
solution of potash is one of the best reagents to isolate the 

cells and to exhibit their nuclei. 
By boiling thin sections of nail 
in a 10 p. c. solution of soda 
the individual cells are demon- 
strated very quickly. Berthold 
proved the lite of a nail cell to 
be four months in the summer 
and five in the winter. 

HAIR. 

Close in this connection comes the hair and its tissues. 
Hairs cover nearly the entire surface of the body, varying in 
size and physical characters in different situations. The hair 
is ordinarily coarser in women than in men, dark hair coarser 
than light. Hairs are very elastic and 
may be stretched one-third more than 
their entire length. They are also 
very strong, one from the head will on 
an average bear a weight of six or seven 
ounces. They can become strongly 
charged with negative electricity by 
friction. They readily absorb moisture 
becoming sensibly elongated. In a 
human hair cut from the head three parts 
are distinguished. First, the cuticle, 
which is composed of thin, flattened, 
quadrangular cells arranged in an im- 
bricated manner. The outlines of these 
cells give to hair its peculiar markings. 
Second, the cortex, or fibrous substance. 
This is best seen in a hair that has been 
boiled in sulphuric acid and then 




FIG. 34. 



Human hair (white.) 
x 500. 



7o 



THE STUDENTS MANUAL OF HISTOLOGY. 



brushed. A few longitudinal lines resemble fibres ; they 
are long, irregular, or spindle-shaped, flattened cells. Third, 
the medulla. This is present only in a portion of the hairs. 
It is not found in the soft, downy hairs of the body, and is not 
always present in the hairs of the head. In size it is equal to 
one-fourth or one-third the diameter of the hair. It is composed 
of small, round or polyhedral nucleated cells. In these cells 
are sometimes seen granules of pigment of various 
colors, although the mass of coloring matter appears 
to be in the cortex. In the medulla are small 
air globules between the innumerable small cells. The 
color of the hair depends upon the color and amount 
of pigmentary matter in the cortex and the amount of 
air in the medulla. In hair that has become gray from old age 
there is a marked loss of pigment, while in sudden blanching 
of the hair the amount of pigment remains normal but the 
medulla becomes filled with air, some entering the cortex also. 
The hair as it lies in its oblique sac 
in the skin has surrounding it an invo- 
lution of the corium, and frequently that 
of the subcutaneous cellular tissue. The 
outer part of the sac is composed of longi- 
tudinally and transversely arranged con- 
nective tissue. 

Internally is the hyaline boundary layer. 
At the bottom this layer forms a papilla 
from which the hair is formed and nour- 
ished. The hair bulb rests on the papilla. 
As the skin is involuted we find its horny 
layer dipping down in the sac to make the 
internal root sheath, while the rete-muco- 
sum forms the external sheath. The 
horny or internal root sheath divides into 
two layers, the superficial layer consists of 




FIG. 35- Cat's Hair. x 400. 



THE STUDENTS MANUAL OF HISTOLOGY. 



71 




FIG. 36. — Human hair, a, the sac. b, its hyaline inner layer. c, the external, d, the inner 
root-sheath, e, transition of the outer sheath to the hair-bulb, f, epidermis of the hair (at f, in 
the form of transverse fibres.) g, lower portion of the same, h, cells of the hair-bulb. i, the hair 
papilla. k, cells of the medulla. I, cortical layer, m, medulla containing air. n, transverse 
section of the latter, o, the cortex. (Frey.) 

vertically arranged non-nucleated cells, and the deep 
layer consists of cells which are nucleated and arranged 
around the hair shaft. While the hair is still within the sac 
there is a double layer of hyaline cells standing obliquely 
around it. The outer layer terminates with the sac, but the 
inner one covers the shaft of the hair throughout its entire 
length. (See above.) Sometimes the inner layer presents the 
appearance of transverse fibres. Hair grows by a cell increase 
from the lower part of the hair bulb. It commences at the 



72 



THE STUDENTS MANUAL OF HISTOLOGY. 




FIG. 37. Transverse section through 
a human hair and its follicle, a, hair, 
b, epidermis of the same, c, inner, 
and d, outer layer of the inner root- 
sheath, e, outer root-sheath, f, its 
peripheral layer of elongated cells, g, 
hyaline membrane of the hair sac. h, 
its middle, and i external layer. (Frey.) 



end of the third or beginning 
of the fourth month of foetal 
life. 

To obtain transverse sections 
of hair it has been recom- 
mended to shave the chin and 
then in an hour repeat the pro- 
cess. This has proved a very 
poor method in our hands. The 
sections are cut obliquely, and 
are very unsatisfactory for 
study. A much better method 
is to tie a number of hairs to- 
gether and dip them in a so- 
lution of gum arabic. Remove 
at once and when the gum is 
dry imbed the bunch and cut 
the sections, or a few hairs may 
be placed between two pieces 
of pith and very satisfactory 
sections cut off-hand with a sharp 
razor. For studying the hair 
sacs sections of the scalp are 
prepared. 



CHAPTER V. 



Connective-tissue Group. 

WHITE FIBROUS YELLOW ELASTIC ADIPOSE TISSUE PIG- 
MENT CELLS CARTILAGE BONE. 

WHITE FIBROUS. 

WHITE fibrous tissue is extensively diffused throughout the 
body. It is arranged in the form of bundles which have a 
wavy appearance more or less marked according to the degree 
of contraction. These bundles may be small and thin, or very 
large and thick and possessed of considerable elasticity. Each 
bundle is composed of minute elementary fibrils which are held 
together by a "cement substance." Acids and alkalies destroy 
the fibrous appearance of this tissue by converting the fibrils 
into gluten or gelatine. In some parts the bundles of connec- 
tive tissue are surrounded by a hyaline sheath so that when 
reagents are applied and cause the bundles to swell up, the 
sheath is torn into transverse portions which rapidly contract 
between the protruding portions of the bundles. This gives 
the peculiar rings or points of constriction. 

The primitive fibrils of our bundle do not divide, neither 
do they anastomose. We find them arranged differently in 
various parts of the body, loosely as in the subcutaneous tissue, 
and then firmly in parallel groups as in tendon. Two kinds of 
cells belong to connective tissue. First the mobile, and second 
the fixed. The mobile, or migratory cells, are lymphoid ele- 
ments which have left their proper channels in the blood and 

73 



74 



THE STUDENTS MANUAL OF HISTOLOGV, 



lymphatics to slowly wander through the tissues. The fixed 
connective tissue cells consist of an oval nucleus surrounded 
by a thin structure of protoplasm which extends out into points 




FIG 38 A, White Fibrous. B, the same atter adding acetic acid. 
C, Yellow Elastic, x 400. 



at the periphery. These processes may be few or many in 
number, short or long, and by these the cells are brought into 
continuity with each other so as to form a net-work. Waldeyer 
describes a large, coarse, nucleated, granular cell found near 
vessels, especially the arteries and called by him " plasma 
cells." 




THE STUDENTS" MANUAL OF HISTOLOGY. 75 

METHODS OF EXAMINING. 

A small piece of subcutaneous tissue is placed on a slide 
and moistened with the salt solution. Bundles of the fibrils 
are seen with their wavy appearance. A few elastic fibres may 
be seen here and there in the field. Acetic acid will cause 

this fibrous appearance to disap- 
pear and the tissue to look like a 
mass of jelly. The cells are seen 
without much difficulty in a speci- 
men of intermuscular fascia. A 
small portion of this is excised with 
the scissors and by the aid of 
needles carefully spread out on a 
dry slide ; the specimen is kept 
moist by occasionally breathing 
upon it. A drop of hematoxylin is 

FIG. 3Q. Connective tissue cells from i j i 1 • i_ 

the penmysium of an ox. x 4 oo. now placed on a cover glass which 
is inverted upon the specimen. A 
drop of acetic acid is placed at the edge of the cover and the 
cells now show to good advantage. Specimens of this tissue 
may be teased from a tendon while fresh or the tendon may be 
hardened in chromic acid and longitudinal and transverse 
sections examined. 

White fibrous tissue is developed from embryonic connec- 
tive tissue cells which are spherical at first, but afterwards be- 
come elongated, then spindle shaped with a nucleus. The 
protoplasm of the original cell is directly transformed into a 
bundle of connective tissue fibres, the nucleus gradually disap- 
pearing. (Boll.) Henley describes another method where the 
embryonic cell produces a peripheral substance in which sub- 
sequently bundles of fibrous tissue are formed. 

YELLOW ELASTIC. 

Yellow elastic tissue is composed of distinct, round, indi- 
vidual fibres which anastomose, divide, have a tendency to 



7 6 



THE STUDENTS MANUAL OF HISTOLOGY. 



curl at the ends, and are not affected by acetic acid. In this 
last respect they are in direct contrast to the white, this enables 
them to be recognized very easily. By their dividing and an- 
astomosing an elastic net-work is formed. 

METHODS OF EXAMINING. 

These fibres are found of large size in the ligamentum 
nuchae of a calf or ox. A small piece is separated thoroughly 
with needles and examined. These fibres are developed di- 
rectly from nucleated embryonic cells. If it is desired, they 
can be preserved in glycerine. 

ADIPOSE TISSUE. 

Adipose tissue is generally possessed of an artery and 
vein and a rich net-work of capillaries. This net-work is usual- 
ly small, in most cases surrounding but one, two, or three of 
the fat cells. The cells are aggregated into groups, each group 
having its afferent and efferent vessels. A fat cell is a spheric- 
al body containing a large fat globule which occupies the 
bulk of the cell. The wall of the cell is very thin and sur- 
rounds the fat on every side. In the cell 
is seen occasionally a nucleus ; this is 
many times obscured from sight, and 
is only recognized after the fat has been 
dissolved out of the cell. 

The connective-tissrie corpuscles are 
transformed into fat cells by having de- 
posited into their interior small fat glob- 
ules which increase in size and number 
until they become confluent in one or two 
large drops. As a result of this the size 
of the cell is greatly increased. When 
the adipose tissue in the body is being 
reduced from starvation, or from other causes, the fat 
disappears from the cells and a clear fluid takes its 




FIG. 40. Adipose Tissue. 
x 200. 



THE STUDENTS MANUAL OF HISTOLOGY. 



77 



place. After a time this too may be removed and 
cell return to its original connective-tissue corpuscle. 



the 



METHOD OF EXAMINING. 

To study this tissue it is only necessary to place a small 
piece on the slide, cover and examine, first with low and then 
with higher powers. Injected specimens are much to be pre- 
ferred. Thin sections are cut from the fresh specimen by the 
aidof the freezing microtome. Sections can be mounted in 
glycerine ; if injected, in Canada balsam. 

PIGMENT CELLS. 

These are much more common in the lower than in the 
higher vertebratse. In the lower animals the connective-tissue 
cells are filled with pigment granules of various colors from a 
jet black to a greenish or gray. Here the cells have long pro- 
cesses which anastomose with each other. The processes con- 
stitute about all of the cell, only a nucleus is present where the 
body of the cell is usually found. These cells are capable of 
^ altering their shape, for when sub- 

^_^4^^^ jected to certain irritants they can 

^Xjmffi^ ( withdraw their pigment processes 
^3pP| jT entirely, becoming changed into a 

f^f ~&w round, spherical body with a central 

/ y^^t^mjjmjl nucleus. This change is under the 

J /r^-»\ control of the nervous system and 

accounts for the rapid changing of 
color observed in many animals. It 
will be understood, however, that the 
contraction of the pigment processes 
does not necessitate the contraction 
4°o of the whole process of the cell. 
Only a portion of the process of the cell is occupied by pig- 
ment. The part containing the pigment is the intercellular 



FIG. 41. Pigmented connective 
tissue cells from mammalian eye 



78 THE STUDENTS' MANUAL OF HISTOLOGY. 

fibrils (Klein) and the part not containing it, the matrix of the 
cell. 

In man, pigment cells are limited almost exclusively to 
the eye. 

The cells with their long processes described above are 
always seen when examining the circulation of the blood in the 
web of a frog's foot. 

CARTILAGE. 

There are three varieties to be studied. First, the hyaline 
with a homogeneous interstitial substance. Second, the 
fibrous, in which the matrix is split up into fibres. Third, the 
reticular. The articulating surfaces of bone are covered with 
a layer of cartilage from -gL- to -^ of an inch thick. In this 
situation it is not covered with a membrane, but with this ex- 
ception all cartilage is covered with a thin vascular membrane 
called perichondrium. 

Hyaline cartilage is composed of nucleated spherical, or 
oval cells in which are occasionally seen small fat globules, and 
of a hyaline matrix. Lacunae are seen of an oval or round 
shape measuring from ^ to ^ of an inch. They are lined 
with a membrane which has been demonstrated to possess 
minute openings (Arnold). These lacunae are filled complete- 
ly by the cells in living cartilage, but after death, and by the 
use of reagents, the cells shrink away from their walls and a 
space is left between them and the walls of the lacunae. These 
cells may be quite close together or they may be separated 
some little distance by the matrix substance. In growing 
cartilage the nuclei of the cells divide, afterwards the whole 
cell, until a number of cells is produced. These cells soon be- 
come separated from each other by a considerable amount of 
matrix derived from their growth. The matrix of this variety 
is a homogenous hyaline substance which yield "chondrin." 
It is firm, structureless, without blood-vessels or nerves, and is 



THE STUDENTS MANUAL OF HISTOLOGY. 



79 




derived from the cells themselves. It is permeated all through 
its substance with fine channels which anastomose with the 
openings in the walls of the lacunae (Arnold). These spaces 

are the lymph channels 
of our tissue. In cer- 
tain pathological con- 
ditions, and in old age, 
the salts of lime are de- 
posited in the matrix of 
this cartilage. Ranvier 
tells us this process 
commences next to the 
cartilage cells. By the 
aid of certain reagents 
the homogeneous ap- 
pearance of the ground-substance of this tissue is destroyed, 
and it is proved to consist of thick rings surrounding 
the individual cells or groups of cells, proving without doubt 
that this part of the cartilage repre- 
sents the formed material of the cells. 
Fibrous cartilage as found between 
the vertebrae, symphysis pubis, etc., 
differs from the first variety in that its 
matrix is composed of bundles of ordi- 
nary fibrous tissue. At the point where 
tendinous tissue passes into fibrous 
cartilage the fibres of the former pass 



FIG. 42. Hyaline Cartilage, x 400. 




FIG. 43. Thyroid cartilage ofthe 

ld i TnJce^-disyctTmea d ns i rf uninterrupted into those of the latter. 

reticular carti- 



chlorate of potash and nitric acid. 
(Frey.) 



In yellow elastic or 
lage as found in the lobe of the ear, 
the ground-work consists of hyaline 
cartilage which is permeated by elastic fibres. These anasto- 
mose and divide to form a reticulated framework. In this 



larynx, epiglottis, etc. 



80 THE STUDENTS' MANUAL OF HISTOLOGY. 

variety the cells are more abundant and surrounded by a 
homogeneous area. 

METHODS OF EXAMINING. 

For the study of hyaline cartilage nothing can excel the 
preparations obtained from the thin cartilage projecting from 
the sternum of a recently killed young newt. Any tissue 
covering the cartilage is easily removed and many times the 
specimen is thin enough for immediate examination. It is 
moistened with a drop of the normal saline solution and ex- 
amined with a %. inch objective. Remove the salt solution 
and add a drop of a 5 p. c. solution of acetic acid. Now the 
nuclei become more granular and distinct. 

Most beautiful specimens are prepared as follows : 

A thin section is placed on a slide and covered with a 
drop of hematoxylin, which is allowed to remain two or three 
minutes, then it is washed off with alcohol. A drop or two of 
acetic acid is added and in a moment washed off with alcohol. 
The strength of the acid used will depend upon the degree of 
coloring imparted to the tissue by the staining. If the color- 
ing was deep, the acid should be of full strength, if not so 
deep, then from a 10 to 20 p. c. solution should be used. By 
this method the matrix is stained but slightly, the cells more 
so, and the nuclei most intensely. The spaces between the 
cells and matrix are now very distinct and the whole specimen 
shows everything to be desired. The sections are best pre- 
served in glycerine. 

Chloride of gold is here highly recommended. The 
section is placed in a 1 p. c. solution for 15 or 20 minutes, then 
exposed to the light in distilled water for 24 or 36 hours, and 
finally mounted in glycerine. The cells are stained violet and 
they are not caused to retract from the matrix, the nuclei are 
colored a reddish tint and the matrix is scarcely stained at all. 

Osmic acid is useful in that it stains all fatty particles black. 



THE STUDENTS MANUAL OF HISTOLOGV. 



A .25 p. c. solution should be employed and the section allowed 
to remain in it for 12 or 14 hours. 

With the other varieties of cartilage the chloride of gold 
method may be employed or they may be examined fresh. 

To show the layers arranged concentrically around the 
cells, the cartilage may be digested in water at about 100 de- 
grees F., or dilute sulphuric and chromic acids, or a mixture 
of nitric acid and chlorate of potash. 

BONE. 

In man bone forms the whole of the skeleton and the ce- 
mentum of teeth. We find this true in most of the vertebrata. 
Histologically we distinguish two parts in this osseous tissue, 
the matrix and the bone cells. This distinction is easily per- 
ceived, if a thin section be placed under the microscope and 
examined by transmitted light. The matrix is firm and brittle 




FIG. 44. Transverse section of bone (man,) a, Haversian canals, b, lacunae. 



c. canahcul 



and impregnated with insoluble inorganic salts. By the action 
of dilute acids the carbonic acid is eliminated from its combi- 



THE STUDENTS MANUAL OF HISTOLOGY. 



nation with the lime which is rendered soluble, while the bone 
becomes soft without changing its form. The soft matrix rep- 
resents the " ossein," which is composed of minute fibrils 
arranged parallel to, or interlacing each other. 

The bone corpuscles are lacunae with long branches, 
canaliculi, by means of which they may anastomose with neigh- 
boring lacunae. Each lacuna contains a nucleated cell of pro- 
toplasm, the bone cell proper. For histological study bone 
may be divided into two classes, compact and spongy. 

In compact bone we recog- 




Haversian canals, 
lamellae. Ill, bone 



FIG. 45, Longitudinal section of bone show- 
ing bloodvessels. (Haversian canals.) x 25. 



nize ; I, 
II, bone 
cells. 

I. The Haversian canals are 
for the purpose of conveying 
blood-vessels and lymphatics. 
They vary in size, but average 
about the jfo of an inch in 
diameter. They may be round 
or oval in shape. -Where the 
bone is most compact near the 
outer surface they are very 
small, but towards the central 
cavity they acquire a large size. 
In a longitudinal section these 
canals may be seen to form 
elongated meshes, communi- 
cating with each other by 
branches given off at acute 
angles or more generally by 
means of short oblique branch- 
es. They open either upon the 
external compact substance of 
the bone or into the central 



THE STUDENTS MANUAL OF HISTOLOGY. 



83 



medullary spaces. They are lined with a delicate mem- 
brane. Around these Haversian canals are seen in transverse 
sections, layers of rings termed lamellae. 

II. These are arranged as follows : 1. Concentrically. 
As many as fifteen lamellae are occasionally counted around 
one canal, but the number varies exceedingly, the smaller 




FIG. 46. Transverse section of bone, showing lamellae, x 50. 



-canals having fewer than the larger ones. 2. Interstitial 
lamellse. These are more or less curved and run in various 
■directions. 3. The circumferential lamella: are disposed 
parallel to 'and in contact with the periosteum externally 
•and limiting internally the large medullary canals. 



8 4 



THE STUDENTS MANUAL OF HISTOLOGY. 



III. The bone corpuscles are found between the lam> 
ellae and are arched to correspond with their curve. They 
are quite numerous. Welcker gives on the average 740 to 
the square millimetre, and Harting 910. They appear as 
dark, black figures with a central body, lacuna, and branched 




FIG. 47. Two bone corpuscles. It will be noticed that many of these canaliculi are not 

connected with the lacunae. They belong to other lacunae not shown in 

the drawing, x 600 

fibres given off on either side, canaliculi ; these communicate 
with others from other cells and thus the lacunae are con- 
nected together. The majority of the canaliculi are given 



THE STUDENTS MANUAL OF HISTOLOGY. 



85 



off at right angles to the lamellae but some pass off in all 
directions. In thin longitudinal sections this is well seen as 
is also their inter-communications. The canaliculi open in 
the Haversian canals, on the surface of the bone, and in 
the large central medullary cavity. In living bone the lacunae 
are completely filled with protoplasmic cellular matter, — ■ 
containing a nucleus and sometimes a nucleolus, — which 
sends prolongations into the canaliculi. Between the lamellae 

of compact bone are 
fibrous bundles im- 
pregnated with lime 
salts and known as 
the " perforating fibres 
of Sharpey." They 
are connected with the 
periosteum from which 
they have their origin, 
and they are present in 
all bone developed in 
connection with the 
periosteum. 

This leads us to a consideration of the membrane sur- 
rounding bone, the periosteum. This is composed of two 
layers. 

The external layer 
consists of a dense, 
firm, fibrous tissue. In 
some parts it covers 
the bone with but a 
single layer of con- 
nective tissue bundles, 

While in of here two or FIG - < 49 " The Sha^pey's fibres, b, of a periosteal lamella 
Willie in OtnerS tWO Or f the human tibia, a, c, lacunae, (from Frey.) 

three layers are recognized. A few blood-vessels supply this 
layer. The internal layer has, in addition to the connective 




FIG. 48. Bone cells from fresh young bone of human 
tibia, filled with nucleated germinal matter, x 600. 




THE STUDENTS MANUAL OF HISTOLOGY. 



tissue bundles, a large number of nucleated cells of various 
sizes. In young growing bone, sharp points project into this 
layer, which are often covered with a layer of nucleated cells,. 
" osteoblasts." 

In the central cavity of long bones and filling them com- 
pletely is a peculiar yellow or red substance called marrow. 
Both these varieties have a large supply of blood-vessels. 
Placed under the microscope the yellow marrow in seen to 
consist largely of fat cells, connective-tissue cells and nucleated 
cells similar in appearance to lymph corpuscles; these are the 
marrow cells. The red marrow as found in the meshes of 
spongy bone contains fewer fat cells and more marrow cells. 
Here are found large, colored, nucleated corpuscles. These 
are probably the intermediate forms between lymph cells 
and colored blood corpuscles. Here also are the large,, 
many nucleated, giant cells of Robin. 




FIG. 50. Cancellated bone., from head of human femur. X25. 



THE STUDENTS' MANUAL OF HISTOLOGY. 87 

METHODS OF EXAMINING. 

For a typical specimen of compact tissue a longitudinal 
and transverse section of one of the long bones of the body 
should be prepared, as for instance, sections from the humeras 
or femur. The bone selected should be entirely free from 
grease and of a pure white color. With a fine saw a thin 
section is cut and transferred to a hone or fine grindstone. 
In this laboratory oil stones are used, each stone measuring 
six inches long, two wide and one thick. The surfaces of 
these hones are freed from grease or dirt by washing them 
in warm soda water. The section of bone is placed between 
the flat surfaces of two of these hones. They are kept con- 
stantly wet with water. The lower hone rests on a table, 
while the operator moves the upper hone over it rapidly, 
and pressing hard upon it at the same time. The more 
force used the sooner will the work be over. These active 
measures are continued until the bone is as thin as a sheet 
of writing paper. Now the force is very slight, just the 
weight of the hone, and the motion is slower and slower. 
The section is ground in this way until it is extremely thin, 
as easily bent as thin paper, perfectly transparent, so much 
so that when wet and placed over the finger, it can scarce- 
ly be seen, so thin that under the % inch only one layer of 
cells can be made out. This whole process need not occu- 
py over twenty or thirty minutes. The section is now trans- 
ferred to a glass slide and thoroughly washed in distilled 
water by aid of a camel's hair brush. It is then removed 
to a clean, dry slide and allowed to dry. If in drying it 
tends to curl, another slide had better be placed over it. 
The Canada balsam used should be hard when cold, — so 
hard that it can be chipped off in flakes with a knife. Ordi- 
nary balsam can be made in this condition by exposure to the 
air for a long time, or better still, by the application oi heat 
for a short time, until the volatile matters are driven oii. 



THE STUDENTS MANUAL OF HISTOLOGY. 



A drop of this balsam, melted, is placed on a warm glass 
slide, also a drop in the centre of a cover glass. The slide 
and cover are kept warm over a flame until the balsam has 
evenly diffused itself. If any air bubbles appear they may 
be removed by touching them with a hot needle or by skim- 
ming them off by drawing the needle horizontally over the 
surface of the drop. The slide is now removed to the table 
and in a moment or two the cover also. When the balsam 
on the slide is slightly cool, but before it is cold, the bone 
is placed upon it. The cover is now inverted over it, and 
pressed against the slide. In a few moments the balsam is 
very hard, when the excess can be chipped off with a knife 
and cleaned by rubbing with a cloth moistened in turpentine. 
If the balsam be too hot when the bone is placed upon it, it 
will run into the lacunae and canaliculi, and the specimen will 
not show to advantage ; if too cold the cover glass can not be 
pressed down tightly. In this latter case the specimen can be 
gently warmed and the cover pressed down. The specimen is 
immediately exposed to the cold, to harden the balsam as soon 
as possible. If successfully treated nothing can exceed the 
beauty of these sections. The lacunae and canaliculi are filled 
with air and surrounded by the balsam. They now appear in- 
tensely black and show to the best advantage possible. For a 
number of years we have followed this method and invariably 
have success. Over a thousand of these specimens are mount- 
ed by students in this laboratory each college year, and a poor 
specimen would be hard to find, notwithstanding students are 
recommended by some authors not to mount this tissue as. 
it is so tedious to prepare and shows so poorly when pre- 
pared. After a little experience the whole preparing and 
mounting need not exceed thirty minutes. For longitudinal 
sections more care is necessary to keep the balsam from 
entering the cavities. It is advisable, therefore, at first not 
to grind these sections quite as thin as the transverse. 



THE STUDENTS' MANUAL OF HISTOLOGY. 89 

To macerate bone a .5 per cent, solution of chromic acid, 
to which has been added a few drops of hydrochloric acid, is 
employed. The bone should be cut in small pieces and the 
amount of the solution used should be very large. In a few 
days sections can be made in any direction with a razor. A 
saturated solution of picric acid, as recommended by Ranvier, 
is very useful. The • pieces of bone should be small and crys- 
tals of the acid should be added from time to time. Fresh 
bones stained exhibit the bone cells, or the bone may be de- 
calcified by chromic acid. Small pieces are immersed in a 
large quantity of the solution which should be very weak at 
first, 1 to 500, and gradually changed every day oi? two for 
stronger ones, until in a week it may reach 1 to 200. 

The bone has been long enough in the mixture when a 
needle can be passed through its middle. Thin sections can 
be made with a razor ; after thoroughly washing in water to 
remove all traces of the acid, they are stained with hematoxy- 
lin and mounted in dilute glycerine. Decalcified bone is used 
to demonstrate Sharpey's fibres. One of the blades of a pair 
of forceps is inserted into the outer surface of the bone and a 
thin strip torn off. Examining several of these strips one will 
find on some the tapering fibres " looking like nails driven 
through a board." The flat bones of the skull are the best to 
use for this purpose. 



CHAPTER VI. 



Teeth. 

A TOOTH may be said to be an enlarged papilla of the mouth 
which has undergone such histological and chemical 
changes that it has acquired a remarkable degree of hardness. 
In the fully developed tooth there are three parts: i, the 
crown, the free part projecting above the gums. 2, the neck> 




FIG. 51. A. Longitudinal section of a tooth, a, enamel, b, dentine. c, cementum. d, pulp 

cavity. B, enamel rods, isolated by acids, longitudinal view. C, transverse view of rods. 

D, the rods or prisms seen in situ. B. C. and DX400. 

3, the fang, the part projecting 
90 



surrounded by the gum. 



THE STUDENT S MANUAL OF HISTOLOGY. 



91 



into the alveolus of the jaw. In the centre of the tooth is a 
canal with an opening at the apex of the root, terminating 
above after entering the crown. It may be simple or multiple, 
depending on the number of fangs to the tooth. The great 
mass of the tooth is composed of a substance much harder 
than bone termed dentine ; covering the crown of the tooth is 
the enamel, while surrounding the fang is a bony substance, 
cementum. 

THE CENTRAL OR PULP CAVITY. 

The central or pulp cavity is completely filled with a soft 
substance known as the dental pulp. This consists of 
connective tissue, nucleated cells, blood-vessels and nerves. 
The nucleated cells are distributed through the mass of the 
pulp but mostly cover it as a distinct cell membrane. They 
are oblong in shape and measure from 12 1 00 to -g^-g- of an inch 
in length and xoVo - m breadth. This membrane, the mem- 
brana eboris, will cling to the walls of the pulp cavity when the 
pulp is removed. The cells composing it were named by 







FIG. 52. A, Transverse section of fang of a bicuspid tooth, x 5. a, cementum. b, dentine. c, 
pulp cavities B, transverse, and c, oblique sections of dentine. X400. 

Wakleyer the odontoblasts. Each cell sends one process 
or more into the tubules of the dentine, while other processes 
unite with those from neighboring cells in the membrane; and 
in the interior of the mass. Thus alt the deep and superficial 
cells are connected with each other and indirectly with the 



92 THE STUDENTS MANUAL OF HISTOLOGY. 

processes in the dental tubes. The vessels form a capillary 
net-work. 

The nerves end in fine non-medullated fibres which are 
distributed at the surface of the pulp between the superficial 
cells. 

Boll observed in the teeth of rodents, macerated one hour 
in a -^ per cent, solution of chromic acid with the membrana 
eboris preserved in connection with the pulp, a large number 
of extremely fine fibres that passed outwards and, in teased 
preparations, accompanied the dentinal processes as fine hairs. 
By their length and direction they appeared to enter the 
dental tubes, and although no traces of them have been satis- 
factorily demonstrated, it is altogether probable that Boll's be- 
lief is the correct one. 

b 




FIG. 53. Section through cementum and periphery of dentine, a, bone cells in cementum. b, 
interglobular spaces, c. fine dentinal tubes at surface of the dentine, x 400. 

It is a well known physiological fact that nerves are more 
sensitive at their terminal points than along their course. 
Dentists find upon operating on the teeth that on reaching and 
cutting the periphery of the dentine great pain is experienced by 
the patient, but as soon as the cutting is deeper the pain is 
materially lessened. This is exactly what would follow if the 
nerve fibres terminated at the ends of the dental tubes, at the 



THE STUDENTS' MANUAL OF HISTOLOGY. 93 

periphery of the dentine. If single nerve fibrils do not thus 
extend into these tubuli, then it would appear they must be 
connected in such a way with the odontoblasts that the pro- 
cesses of the latter are capable of transmitting the properties of 
the former. We are most favorably inclined to accept the 
views of Boll. 

THE DENTINE. 

The dentine presents a yellowish-white fibrous appearance 
and is one of the hardest constituents of the body. It has a 
firm matrix and extremely fine canaliculi, the so-called, den- 
tinal tubes. At the larger ends their average diameter is 
about 4g 1 00 of an inch and they are separated from each other 
by two or three times their width of matrix substance. They 
commence by circular openings on the walls of the pulp cavity 
and extend radially outwards, making spiral turns, like a cork- 
screw, on their way; this twisted appearance is easily seen in 
decalcified specimens. While extending outwardly to the 
enamel or cement they give off numerous branches by which 
they and their contents anastomose freely. At the surface of 

the dentine these are ex- 
tremely fine and many of 
them terminate in larger 
or smaller cavities at this 
point known as the inter- 
globular spaces of 
o, ■ •• _. Czermak. 

FIG. 54. Showing membrane lining dentinal 

tubules. (Boii). The tubes are lined with 

a sheath, the dentinal sheath, which is readily seen in softened 
specimens. In these sheaths lie the dentinal fibres of Tomes. 
They are the greatly elongated processes of the odontoblasts 
with perhaps nerve elements. They are solid and homo- 
geneous, and easily stained with carmine. In old teeth these 
fibres evidently do not extend to the finest terminal points of 
the tubes, although in the young they certainly do. 





94 TH E STUDENTS MANUAL OF HISTOLOGY. 

In that part of the dentine which is just beneath the 
cementum and sometimes in that just beneath the enamel, 
there is a large number of spaces, interglobular spaces, the 
granular layer of Purkinje. 

Many of the dentinal tubes end in these spaces. They 
have a ragged outline and many 
short pointed processes. They 
denote an arrest in the develop- 
ment of the tissue at that point. 
Dental tubes pass through them 
uninterrupted (Tomes). Besides 
the tubes there is a substance with- 
in them which takes carmine stain- 

FIG. 55. Odontoblasts, a, portion [ n cr only with difficulty. In a 

of dentine, b, two odontoblasts which ° 

pass with their processes through a por- transverse section of dentine rings 

tion of the dentinal canals and protrude . 

from them at c. (Beaie). are seen concentric with the cavity 

of the pulp. These rings may be due either to curves of the 
dental tubes, each tube curving at the same distance from the 
surface or to rows of interglobular spaces. 

CEMENTUM. 

Cementum is absent from the crown of the teeth of man. 
(See cuticle of the enamel.) It commences just over the 
enamel at the neck of the tooth and forms a thick coating over 
the fangs. At the end of the root it is often found thickened 
by an exostosis. It is composed of a matrix identical with 
bone, and of lacunae and canaliculi. The latter are much 
longer and more numerous than in true bone. They communi- 
cate directly with some of the dental tubes and also with each 
other. Some lacunas are seen with sharply defined contours 
and with short processes. They are the " encapsuled lacunae " 
first described by Gerber. In this way a single lacuna or sev- 
eral of them, may be enclosed. Here in the cementum, as in 
bone, are the penetrating fibres of Sharpey, representing calci- 



THE STUDENTS MANUAL OF HISTOLOGY. 95 

fied bundles of connective tissue. Where the cementum com- 
mences at the neck of the tooth no lacunae are found and it 
appears structureless. 

THE ENAMEL. 

Upon the outer surface of the dentine of the crown of the tooth 
is the enamel, the hardest substance of the body. It is com- 
posed of closely crowded polyhedral prisms, the enamel prisms, 
enamel columns, enamel rods. They are about 3 J 00 of an inch 
in diameter and mostly pursue a direction from the dentine 
toward the surface. They are in close contact with each other, 
and so far as can be demonstrated there is no intervening sub- 
stance to unite them together, although the action of certain 
reagents in isolating the rods leads one to suspect here, as else- 
where, a "cement substance." Nearly all the fibres run the 
whole length of the enamel but some are seen in the outer 
portions which do not penetrate far into the interior. 
Transverse lines or striations are seen on isolated fibres as well 
as continuous over adjacent ones. Hertz believes that these 
lines represent an " intermittent calcification " of the fibre. 
Tomes and Waldeyer think that they are due to varicosities in 
the individual fibre. It is a very remarkable appearance 
and difficult to account for. If hydrochloric acid be 
added to the fibres after they have been isolated, they will 
break up into small cubic fragments of about equal size, corre- 
sponding to the striations on their surface. With the exception 
of these striae, the enamel rods appear perfectly homogenous, 
yet it is observed that acids act upon the central part of the 
fibre, before they do on the periphery. This is readily under- 
stood when the formation of the enamel is understood. The 
hardening salts are deposited first in the periphery of the cells 
and gradually reach the centre, so that in immature fibres may 
be seen a central canal. Soon this difference is obliterated as 
calcification progresses; but when the acids act upon them this 



96 THE STUDENTS' MANUAL OF HISTOLOGY. 

action is reversed, the more recently deposited calcined sub- 
stance is sooner affected. 

There are coarser striations, consisting of a series of con- 
centric lines crossing the enamel fibres. They are of a brown- 
ish color and are known as the "brown striae of Retzius." It 
is possible that they mark the different stages of the growth of 
this structure. While one end of the fibre is implanted in de- 
pressions in the dentinal surface, the other terminates as a free 
end to form part of a beautiful hexagonal mosaic. 

THE CUTICLE. 

Covering the surface of the enamel is an exceedingly tough 
membrane, the cuticle of the enamel, Nasmyth's membrane. 
In thickness it is not more than 5 * 00 to 35 ^ 00 of an inch. In 
young teeth this is easily detached after slight action of hydro- 
chloric acid, but it is doubtful if it exists in the teeth of the 
adult. Although very tough and unaffected by acids, yet it is 
not so hard as the enamel and is on this account generally 
worn away. Silver staining shows it to be composed of cells 
of an epithelial type. On its under side are the indentations 
for the reception of the free ends of the enamel fibres. Tomes 
regards this cuticle as a thin covering of young and incomplete 
cementum. 

METHODS OF EXAMINING. 

Sections of unsoftened teeth can be made in any desired di- 
rection, ground and mounted precisely as recommended for 
bone, giving the very best results. The methods 
for softening teeth are the same as those for softening bone. A 
10 per cent, solution of hydrochloric acid is generally useful. 
If this solution be strengthened the dentinal substance will be 
destroyed and the sheaths lining the tubes will remain for a 
considerable length of time. Only young developing teeth in 
a fresh condition should be subjected to the action of acids for 
the purpose of isolating the enamel rods. Their transverse 
lines may be seen by adding muriatic acid. 



THE STUDENTS MANUAL OF HISTOLOGY. 97 

The dental pulp is studied by using a reagent that softens the 
parts around it, at the same time that it hardens the pulp itself. 
Such a reagent is picric acid. The fresh tooth is broken open 
by the blow of a hammer and placed at once in a saturated 
solution of the picric acid. More crystals of the acid are 
added from time to time and the tooth is frequently stirred in 
the mixture in order that fresh parts of the solution may come 
in contact with it. As soon as the tooth is soft enough to 
allow a needle to pass through it, it is transferred to alcohol. 
The alcohol is changed daily until it fails to be colored by the 
acid. Thin verticle sections are cut with a razor, stained 
n hematoxylin, and mounted in glycerine. 



CHAPTER VII. 



Muscle. 
1\ /TUSCLE may be divided into two general classes: 



I 


Striated, 


i. 


Xon-striated, 


2 


Striped, 


2. 


Smooth, 


5 


Fibres of animal life, 


3- 


Fibres of organic life 


4 


Voluntary, 


4- 


Involuntary, 


5 


Responds rapidly. 


5- 


Responds slowly. 



Thus there are five different terms applied to each of the 
classes. Some of them are based upon histological and others 
upon physiological distinctions. 

There is one muscular organ in the body that cannot be 
classed with either of these divisions. It not only possesses 
properties belonging to both, but has in addition characteris- 
tics not found in other muscles. The heart deserves a place by 
itself and will be treated apart from striated muscle, although 
its intimate structure is so nearly identical with it. In study- 
ing striated muscle the unaided eye at once discovers a thin 
membrane surrounding the whole muscle and sending pro- 
longations into the body, giving the familiar appearance of a 
fine or coarse grained muscle. If a muscle be cut transversely 
this membrane w T ill show to good advantage. The external in- 
vesting membrane consists of a more or less dense connective 
tissue known as the perimysium, while the portion running 
through the muscle, dividing it into compartments, is called 
the endomysium. Each of these compartments is a fasciculus, 
and a fasciculus is a bundle of small fibres, the cut ends of 



THE STUDENTS MANUAL OF HISTOLOGY. 



99 



which are seen in the figure as small dots. These fibres may 
extend through the whole length of the shorter muscles, but 
usually in the" skeletal muscles they are only from 1^2 to 2 

inches in length, although this 
varies greatly in the same muscle 
and in different muscles. The 
diameter of the fibres is also of 
varying size from the thickness of a 
single contractile disc, to the ^ ¥ of 
an inch in man, and to a very much 
larger size in some of the lower ani- 
mals. Their diameter will average 




FIG. 56. Transverse section of 
small muscle of a frog. a, penmysiun 
b, endomysium. c, cut ends of muse 
fibres, showing as dots, x 15. 



not far from the -g-^- of an inch. 
This diameter is said to be much less in the female, but prac- 
tical experience will not warrant the assertion. These fibres 
end rather abruptly, the sarco- 
lemma extending over the end of 
each fibre and becoming lost in 
the inter - fibrillar connective 
tissue. The sarcolemma is a 
transparent, homogeneous, very 
thin and highly tenacious mem- 
brane closely investing each 
muscle fibre. It is invisible in 
fresh muscle, but is easily de- 
monstrated by the aid of re- 
agents. Figure 57 shows this 
membrane extending from one 
end of the broken fibre to the 
other. To obtain this view a 
small piece of frog's muscle was 
teased and while looking through 
a dissecting microscope, pressure 
was made with a needle over one of the fibres. The muscle 




FIG. 57. Sarcolemma of muscle /frog's), 
A. a, ends of a broken fibre, b, sarcolemma. 
x 35. B, Showing sarcolemma, more highly 
magnified. 



THE STUDENTS MANUAL OF HISTOLOGY. 



substance was broken and then contracted either way, leaving 
the sarcolemma intact. By staining with carmine the mem- 
brane was sufficiently colored to enable us to procure good 
micro-photographs of the specimen. Just beneath the sarco- 
lemma are the numerous nuclei of 
the muscle fibre. They are situ- 
ated between the muscle substance 
and the sarcolemma, and do not 
form a part of the latter, neither is 
the sarcolemma developed from 
these nuclei, but from others, no 
trace of which can be seen in the 
adult muscle. According to Klein 
each nucleus contains an intra- 
nuclear fibrillar net-work. They 
are much more numerous in 
young, growing muscle. Rollett 
describes the nuclei found in 
muscles of the amphibia, fishes 
and birds as existing within the 
muscle substance, a condition 
similar to that found in the heart of man. 

These nuclei are easily demonstrated by adding dilute 
acetic acid to a fresh specimen, or by employing one of the 
several staining fluids. -They are often seen surrounded with 
a border of finely granular substance. A muscle fibre is di- 
vided into two substances by broad dim bands and bright nar- 
row ones. The former is the contractile part of the fibre and 
is composed of contractile discs, while the narrow bright bands 
correspond to the interstitial discs. During contraction the 
first become more transparent, thinner in their longitudinal di- 
rection and correspondingly thicker transversely. The second 
become more opaque. At figure 59 a, is seen a contractile disc, 
while b. represents the interstitial disc. Thus in living muscle 




FIG. 58. Striated muscle fibre of the 
frog. The nuclei stained with haematoxy- 
lin. x 200. 



THE STUDENTS MANUAL OF HISTOLOGV. 




it is seen there are no longitudinal striae. By studying one of 
these contractile discs more carefully it becomes differentiated 
into thin oblong rods, each rod the length of the disc. Each 

of these rods represents a single 
sarcous element, which is the 
anatomical element of the con- 
tractile disc. 

These sarcous elements are 
arranged so close to one another 
during the life of the muscle, 
that they appear as one, and the 
disc was said to be homoge- 
neous. However, by the use of 
reagents, or many times spon- 
taneously, during and after life 
they become separated when a 
fluid substance is pressed out 
which appears to be identical 
with the myosin discovered by 
Kiihne. Now if alcohol be used 
for hardening the muscle, the sarcous g 

elements will be arranged endwise, and 
as a result of these elements being 
placed end to end, we have the appear- 
ance of long slender fibrils, the primi- 
tive fibrillar. If, however, in the place 
of the alcohol, hydrochloric acid be used, 
then the sarcous elements appear 
arranged sideways and we have the 
transverse discs. A muscle fibre then is 
either a bundle of primitive fibrils or of 
transverse discs which ever way we look g^JSgt^JS, 

Unon it ^' ,on S l<uc ' lna ' f'bms. Prepared 

ujju ll " from separate specimens, x 300. 

Very intimately connected with the sarcolemma of a fibre, 



) 

uAumtuiAnil, 
miipiiiHinmi 

wirauuinm 



FIG. 59. Muscle fibre, a, contractile disc. 
b, interstitial disc, c, sarcous elements, d, 
transverse membrane of Krause. n, nuclei, s, 
sarcolemma, (Klein.) 





THE STUDENTS MANUAL OF HISTOLOGY. 



are membranous septa which stretch across the muscle at regu- 
lar intervals. These septa are the transverse membranes of 
Krause. They divide the fibre into a number of equal sized 
compartments, "known as muscle compartments." This mem- 
brane of Krause passes directly across the fibre midway be- 
tween two contractile discs, dividing the intervening inter- 
stitial disc into two equal parts. Each of these parts is known 
as a lateral disc, each disc belonging to different muscular 
compartments. A small granule is found in some muscles di- 
rectly at the end of each sarcous element. This arrangement is 
so constant in some muscles, that it has been given a name, the 
"granular layer of Flogel." A transverse section of these 
sarcous elements presents a fine granular appearance, leading 
one to believe that they are composed of most minute fibrils. 
It is certain that they are not optical units, but consist of 
minute doubly refractive elements, the "discliaclasts of Briicke." 

A muscle then is a collection of fasciculi. 

A fasciculus is a collection of fibres. 

A fibre is a collection of muscle compartments. 

( Transverse membranes of Krause. 

A muscle compartment J Sarcous elements. 

is a collection of j Myosin, and sometimes the 
[ granular layers of Flogel. • 

This kind of muscle is found in all the skeletal muscles 
of the body, in the muscles of the oral cavity, pharynx, larynx, 
oesophagus, lower part, of the rectum, diaphragm, middle and 
outer ear, sphincter vesicae, part of muscles of the prostate, and 
modified in the heart. Although a few of the striated muscle 
fibres of the body divide, yet such is not the rule. Aside from 
these few muscles the heart presents distinctive characters, 
particulars in which it differs histologically from the ordinary 
striated muscles described above. First, the fibres have no 
sarcolemma; second, they are smaller; third, they divide; fourth, 
they anastomose; fifth, they are divided into nucleated cells; 
sixth, the nucleus is within the muscle substance of each cell. 



THE STUDENTS MANUAL OF HISTOLOGY. 



103 



Figure 61 represents some of these peculiarities. The 
fibres are much smaller in some parts of the heart than in 
others. In examining a transverse section some fibres will be 

found very small indeed. 
These small fibres are the ends 
of one of the divided fibres, 
and when it is remembered that 
they frequently divide and ter- 
minate in a pointed end, this 
great irregularity in size can be 
readily accounted for. At 
quite regular distances the 
fibres are crossed with a faint 
line, and midway between two 
of these lines is a nucleus which 
is situated within the substance 
in the centre of the cell. Many 
times these cells are so arrang- 
ed that on a thin section, it ap- 
pears that the end of one cell 

microtome and stamed. x 150. j s pl aCe d JUSt Opposite the 

centre of another near it, so that the ends of the cells look not 
unlike a series of steps. 

Meyer tells us that the more a muscle works the deeper is 
its color, but according to Ranvier there may be well defined 
structural differences between the pale and the deeply colored 
muscles. 

If the diaphragm be examined a great number of large 
nuclei or "muscle cells" will be found. They may be in suf- 
ficient numbers to form a nearly complete layer around the fibre. 
All fibres do not seem to be affected alike in this respect. The 
work of the diaphragm must necessitate a great amount of 
waste and repair, hence the large number of bioplasts. 

The second class, involuntary, unstriped muscle, is widely 




FlG. 61. Muscle from the heart of man, 
prepared from fresh specimen, cut with freezing 



io4 



THE STUDENTS MANUAL OF HISTOLOGY. 



diffused throughout the body. (See Strieker, pp. 150, 151.) 
This tissue is aggregated into larger or smaller bundles and is 
composed of elongated spindle-shaped cells held together by a 




FIG. 62. Muscle from diaphragm with large number of bioplasts. (Klein.) 

transparent semi-fluid substance identical with that which 
unites epithelial and endothelial cells. The cell is composed 




FIG. 63. Muscle cells. A, transverse sections through bundles of smooth fibres. B, 

cells from small artery of gumea-pig. C, cell from intestine of man. D, cell 

containing far globules (uterus). E, cells from artery (man); x 400. 

of a longitudinally striated substance in the centre of which is 
a nucleus not infrequently multiple, and usually in the middle 



THE STUDENTS' MANUAL OF HISTOLOGY. 105 



of the long axis of the cell, or in the thickest part of it, which 
may bring the nucleus nearer one end than the other. The 
nucleus is usually oblong and is composed of a fine net-work 
of fibrils which anastomose (Klein) at the poles of the nucleus 
with the bundle of fibrils composing the central part of the 
cell, the true contractile substance. 




FIG. 64. Non-striated muscle cells, (after Klein.) 

Each cell is surrounded by a fine sheath, which shows a 
transverse linear marking, especially if the cell be examined in 
a contracted state. The ends of the cell are drawn out into 
fine points, and in the arteries and veins the extremities are 
frequently branched. The longest and thickest cells are found 
in the walls of the intestine, the shortest in the arteries, the 



106 THE STUDENTS' MANUAL OF HISTOLOGY. 

thinnest in the tubes of the sweat glands (Klein.) Fat gran- 
ules are frequently imbedded in the cells. This is well seen if 
some of the cells be examined from the uterus a few weeks 
after delivery. While some will be filled with fat, others will 
be nearly destroyed by the degenerative process. Granules 
are nearly always present at the two ends of the nucleus. 

METHODS OF EXAMINING. 

To examine microscopically the general appearance of 
striated muscle, a small fasciculus may be taken from the 
body of any of the vertebrates, and by a slight amount of 
teasing in some normal fluid, good views are obtained. How- 
ever, it is better to remove from the under side of the lower 
jaw of the frog one of the thin flat muscles so suitable for 
study. The frog should first be decapitated or pithed and the 
muscle removed carefully without teasing or straining. The 
tissue should be placed on the glass slide at once and moisten- 
ed with blood-serum or normal saline solution. Very satis- 
factory views of the transverse striations and in some cases of 
the longitudinal striations will be obtained in this way. If the 
individual fibres are desired, they are easily separated from each 
other by the aid of needles. The nuclei can be recognized after 
the addition of dilute acetic acid. The sarcolemma so closely 
surrounds the muscular elements that it is not visible by the 
ordinary methods of examination. Yet many times in teasing 
the muscle, some of the fibres have been pressed upon and 
broken, and the contractile substance has contracted at either 
end. leaving the clear transparent sarcolemma as seen in 
figure 57. If water be added to a fresh specimen it will soon 
pass through the delicate sarcolemma, causing it to separate 
from the tissue, so that there is a transparent border at the 
edge of the fibre. Many times, too, the sarcolemma will bulge 
out at the end of a fibre in the form of a little pouch. To 
study farther, some of the tissue may be placed for a few days 
in a .2 per cent, solution of hydrochloric acid, then thesarcous 



THE STUDENTS MANUAL OF HISTOLOGY. 



107 



elements will appear arranged sidewise into transverse discs, 
each disc equalling in length a single sarcous element, and in 
width the same as the muscle fibre. At the same time place a 
specimen in a .5 per cent, solution of chromic acid. If some of 
the tissue be placed in Miiller's fluid for a couple of weeks or 
longer, but slight teasing will cause the muscle fibrils to fall apart. 
Alcohol and chromic acid will cause the sarcous elements to 

become arranged longitudinally, giv- 
ing the appearance of longitudinal 
fibrils, each fibril being just the 
width of a single sarcous element, 
and as long as the muscle fibre 
itself. To demonstrate the relation 
of muscle to tendon, a small shred of 
muscle with its tendonous attach- 
ments must be placed from 20 to 30 
minutes in a 35 p. c. solution of pot- 
ash, when the appearance seen at 
figure 65 will frequently be observed. 
It will be noticed that the sarco- 
lemma is still intact, but that the 
fibres of the tendon have become 
separated from the muscle fibre. 
There has been no teasing or injuring 
of the tissues, and one is forced to believe that the two were 
cemented together, and that the potash solution dissolved this 
cement. It seems safe to assert that muscle is united to tendon 
by a cement, which is dissolved by a 35 p. c. solution of potash 
in from 15 to 30 minutes. The examination of muscle for 
trichinae is very simple. Small shreds of the muscle should be 
teased with needles in some normal fluid media, and examined 
at once with a low power; one giving 50 diameters will be suf- 
ficient at first, although for a more careful examination one oi 
250 or 300 diameters should be employed. Thin sections can 




FIG. 65. Termination of muscle in 
tendon, from tail of young mouse, a, 
muscle fibre, b, sarcolemma. c. ten- 
don, x 50. 



io8 



THE STUDENTS MANUAL OF HISTOLOGY. 



be made with a razor through the trichinous muscle hardened 
in alcohol, using the proper care that the sections be made in 
the direction of the fibres. The worms are seen coiled up as 




FIG. 66. Trichinous muscle. A, from psoas muscle of hog. B, encysted trichina 
from arm of man. B, x 35. 

in figure 66. They may be found in any of the transversely 
striated muscles with the exception of the heart. They are 
most frequently found, however, in the diaphragm and muscles 
of the jaw and neck. They are in greatest abundance at the 
tendonous extremities of the muscles, for they are here pre- 
vented from moving farther. In the hog, fragments of muscle 
should be examined especially from the ham and tenderloin. 
They are usually found arranged spirally just beneath the sar- 
colemma. This spiral arrangement gives them their specific 
name, trichina spiralis. They were discovered in January, 
i860, by Professor Zenker of Dresden. In 1864 Professor 
Dalton counted the number of trichinae in a piece of muscle 
^ inch square and Jg- inch thick, and found 12. This would 



THE STUDENTS' MANUAL OF HISTOLOGY. 



109 



give about 85,000 to the cubic inch. In another specimen of 
the same size he found 29 trichinae, giving again in round 
numbers 208,000 to the cubic inch. The trichinae in half a 
pound of infested meat would be sufficient in a few days to 
develop the extraordinary number of 30,000,000. When it is 
remembered that each of these worms must puncture the 
mucous membrane rn its way to the muscles, it is readily un- 
derstood why they should occasion such notable disturbance. 
As found in muscles they are usually surrounded by a cyst 
containing granules or calcareous matter. In size they aver- 
age about -Jq- inch in length and ^fa inch in thickness. They 
retain their vitality in the encysted state for a great length of 
time. 

Muscle sometimes becomes streaked with fat when it can 
be examined either fresh or after being treated with Miiller's 




FIG. 67. 1 A, Matty infiltration of heart (man). X75. B, fatty degeneration of muscle 
from arm of boy, amputated on account of paralysis of three years standing. 

fluid or chromic acid. When the fat is confined to the con- 
nective tissue between the muscle fibres as in obesity, nothing- 
serious can result from it, unless in some particular organs- 



IIO THE STUDENTS MANUAL OF HISTOLOGY. 



when it may cause a dilatation and weakening from pressure. 
A specimen of fatty infiltration is seen at figure 67. 

When the fat molecules are arranged in rows correspond- 
ing to the longitudinal striae, they usually increase in number 
until all the contractile substance disappears and the muscle 
fibre becomes transformed into a row of fat cells, the fatty de- 
generation causing a complete wasting of the muscle. Non- 
striated muscle cells undergoing this fatty metamorphosis are 
found in the uterus a few weeks after delivery, when in order 
for this organ to become reduced to its previous size many of 
the cells become thus broken down and carried out of the 
body. Striated muscle is best preserved in dilute glycerine, 
equal parts of glycerine and water, — which has been slightly 
acidulated by acetic acid. The glycerine will have the effect 
of causing the transverse striae to show exceedingly well, aside 
from being a most excellent preservative fluid. Muscle may 
be preserved in Canada balsam also, and always should be 
so mounted if the specimen is to be examined by polarized 
light. For the purpose of studying the spindle cells of 
involuntary muscle, a piece of the organ containing it, as 
the bladder of the frog, is placed in a very weak solution 
of bichromate of potash (1 to Soo) for 'orty-eight hours. 
At the end of this time slight teasing with needles will be 
sufficient to separate some of the cells from the large piece. 
Dilute nitric acid, 20 or 25 p. c. solution, does not fail to 
give good results. The specimen is allowed to remain in the 
acid 30 to 36 hours, when, by teasing in water each cell can 
be brought clearly into view. Before teasing, the tissue may 
be stained to advantage with haematoxylin. By removing the 
epithelial cells from the inner surface of the bladder of the 
frog, by washing and brushing with a camel's hair brush, and 
by staining with picrocarmine or haematoxylin, most beautiful 
specimens can be obtained. A specimen mounted in glycer- 
ine and treated as just described, is in the author's posses- 



THE STUDENTS MANUAL OF HISTOLOGY. 



sion, showing the nuclei of the cells, the stained blood-vessels, 
and the blood-corpuscles with stained nuclei in the vessels. 
Nitrate of silver affords the best exhibition of the arrange- 
ments of the cells. About .5 per cent, solution is allowed to 
come in contact with the tissue for two or three minutes 
only. This is washed off with distilled water and the speci- 
men is placed in dilute alcohol and exposed to the direct 
rays of the sun. In a few minutes it can be mounted in 
glycerine, when the outline of each cell will be distinctly 
seen. A one or two p. c. solution of acetic acid will show 
quite distinctly the individual cells, only a few minutes im- 
mersion being required. Weak solutions of chromate of am- 
monia are recommended by Klein. 



CHAPTER VIII. 



Blood-Vessels. 

THE blood is conducted from the Heart by highly elastic 
arteries with a circular muscular element, which relatively 
increases in thickness as the arteries diminish in size. It is 
returned to the heart by the less elastic veins which have a 
variable muscular element. Between the two systems of ves- 
sels are the capillaries of exceedingly small but variable size. 

THE CAPILLARIES. 

The finest capillaries in the 
body are barely sufficient to al- 
low the passage of the blood- 
corpuscles, one after the other, 
often so small as to compress 
them and change their form. 
They may be said to vary from 

iroVo to g^oT of an incn in 
diameter. In the nervous tis- 
sue and retina they are found 
the smallest, in mucous mem- 
branes they are of medium size, 
while in the bones and glands 
they are the largest. They do 
T n ?j 68 -«. c T!L ary t jror ? mes ^ nt f ,un \ not diminish or increase in size 

Treated with nitrate of silver and stained 

with haematoxyiin. a, ceii plates, u, nu- as d the arteries and the veins, 

clei. s, stomata. x 40a 

112 




THE STUDENTS MANUAL OF HISTOLOGY. 



JI 3 



for they form a plexus of vessels of nearly uniform diameter, 
inosculating in every direction. Their average length is about 
■^g- of an inch. Although their diameter is so small and their 
length so short, yet the number is so large that their capacity 
is immense. It has been stated that the entire capacity of the 

capillary system is a number of 
hundred (400 to 800) times as 
great as that of the whole ar- 
terial system. These estimates, 
however, partake of the curious 
and are mere suppositions. 

Without the aid of reagents 
the structure of the capillaries 
appears very simple. A few 
nuclei with nucleoli are seen 
scattered along the walls of an 
elastic hyaline membrane. Ni- 
trate of silver dispels this illu- 
sion and resolves this homo- 
geneous membrane into a single 
layer of nucleated ceil-plates, 
united together by a " cement 
substance ," which is stained a deep black by the solution. 

If the capillaries become distended in any way, this ce- 
ment is liable to give way and minute openings appear, which 
after a time may become enlarged into stomata. These open- 
ings may be present in the capillaries when they are not dis- 
tended, but as a rule in this condition of the walls of the ca- 
pillaries these "stomata" are not true openings, being covered 
with the cement substance. 

Through these stomata the white corpuscles migrate and 
the red find an exit, being forced out passively. Purves, proved 
that the white corpuscles migrated through these openings, by 
staining capillaries through which emigration had been going 




FIG. 69. Capillary vessels and fine 
branches of the mammalia, a, capillary ves- 
sel from the brain, b, from a lymphatic 
gland, c, a somewhat larger branch with a 
lymph-sheath from the small intestine, and 
d, a transverse section of a small artery of a 
lymphatic gland. (Frey.) 



H4 



THE STUDENTS MANUAL OF HISTOLOGY. 



on. In some of the larger capillaries there is an outer sheath 
of connective-tissue cells surrounding this single layer of 
epithelial cell-plates. This layer forms a reticulum, in the 
meshes of which are lymphoid elements. 

THE ARTERIES. 

Passing now to the larger vessels a gradual increase in 
diameter is observed, and transversely arranged nuclei are 

seen. This is the very 
commencement of the 
muscular layer, and marks 
it as a commencing ar- 
tery in contradistinction 
to a capillary. If a me- 
dium sized artery be ex- 
amined as directed below, 
four layers will be recog- 
nized. The most internal 
endothelial layer consists 
of a layer of flattened 
nucleated endothelial 

cells, rendered visible by 
nitrate of silver staining. 

By endothelium is un- 
derstood a layer of flat 
cells which covers any 
membrane not a mucous 
membrane or one lining 
the cavity or canal of a 
secreting gland. They 

70. Capillanes of injected muscle of cat xxoo. yary ^ j^ shapean d 

outline, are held together by a " cement substance " and are 
demonstrated by the aid of a .25 to .5 p. c. solution of nitrate 
of silver. 




THE STUDENTS MANUAL OF HISTOLOGY. 



115 



External to this layer is a longitudinally striated mem- 
brane, the hyaline elastic coat. The net-work of elastic fibres 
is arranged parallel to the long axis of the vessel. The third 
coat from within, the intima, is termed the middle layer of un- 
striped muscle. The cells are arranged for the most part 

transversely. It is the most 
conspicuous of all the coats in 
all the arteries and is very 
distinct in the larger ones. The 
muscle cells first formed only a 
single layer, but they gradually 
increased until now they con- 
stitute an individual coat. In 
most of the arteries there is a 
fine granular connective tissue 
and a few elastic fibres between 
the muscle cells. Some of 
these cells are arranged ob- 
liquely, or even longitudinally. 
In some arteries there are no 
muscle cells whatever. The 
fourth, or most external coat, 
the adventitia, is composed of 
connective tissue with longitudinally arranged cells. Between 
this and the intima, in the larger arteries, there is an elastic 
membrane, the external elastic coat. It is composed of a net- 
work of fine elastic fibres. The adventitia is relatively very 
thick in small arteries, being as thick as the muscular layer. 
In large arteries it is not nearly as thick, and at the commence- 
ment of the aorta, it is a very thin plate. 




FIG. 71. . ransverse section of the walls of 
an artery, a, lining, endothelial layer, b, 
elastic layer, c. muscular layer, d, con- 
nective-tissue layer, x 100. (Quain.) 



THE VEINS. 



Commencing at the capillary there is observed, first, be- 
side the endothelial layer, not a layer of muscle cells as in the 



n6 



THE STUDENTS MANUAL OF HISTOLOGY. 



artery, but a layer of a fine longitudinal net-work of fibres. 
The cells of the endothelial layer are shorter and broader, and 
are not as fusiform in shape as the corresponding layer in 
arteries. The adventitia is about the same as that in the ar- 
teries. In a large number of the veins, muscular tissue ' is 
found in this external coat. The whole walls are thinner than 







FIG 72. Blood-vessels of the stomach of a cat. 

in arteries of corresponding luminae, and the yellow elastic tis- 
sue that gives to the large arteries their thick walls is so 
scanty in the veins that when they are cut across they collapse 
and their cavity is obliterated. The valves of the veins are 
folds of the intima and part of the muscular medium, although 
some veins are entirely without this muscular medium. Arn- 
stein and Steida claim that the trunks of the venae pulmonales 
have striped muscle in their walls. Steida says there is an in- 
ner circular and outer longitudinal coat continued from the 



THE STUDENTS MANUAL OF HISTOLOGY. 1 17 




FIG. 73, Two villi from ileum of infant, x 100. 




FIG. 74. Blood-vessels of human lung, a, larger vessels, b, cap llary net-work, x 400. 



n8 



THE STUDENTS MANUAL OF HISTOLOGY. 




kidney. 



c, glo- 



muscular walls of the left 
auricle. The arteries some- 
times terminate in veins with- 
out the intervening capillaries, 
as in the tip of the nose, fingers 
and toes, and matrix of nails 
(Smith.) In the cavernous tis- 
sues of the genital organs there 
are large wide sinuous spaces, 
the walls of which are com- 
posed of elastic and unstriped 
muscular tissue. The arteries 
convey blood to these spaces 
and the veins carry it back. 




^IG, 76. Blood-vesse s beneath mucous membrane of intestine of infant. 



THE STUDENTS MANUAL OF HISTOLOGY. 



II 9 



The walls of the blood-vessels are supplied with quite a 
rich plexus of capillary blood-vessels which penetrate the 
external layers, but never, the internal. They are called 
the " vasa-vasorum " and are in nowise connected with the 
vessels on which they are distributed. They arise from some 
vessel at a considerable distance from their point of distribu- 
tion and supply the walls with nutritive materials. 

Nerves are freely distributed. 

METHODS OF EXAMINING. 

The walls of capillaries can be studied best 
by isolating some of the vessels of the pia mater. A small 
piece of brain substance is clipped from the exterior of a con- 
volution with the pia mater attached. The section is removed 
to a slide with the pia mater on the glass. By aid of a camel's 
hair brush the cerebral matter is washed away and a drop of a 
.5 per cent, silver solution added. In two or three minutes 
this is removed and distilled water added. The specimen is 

exposed to the light 
until it is colored 
brown, when it is 
placed in glycerine 
and mounted. The 
capillaries in the 
'mesentery of the 
frog, or tail of the 
tadpole, can be de- 
monstrated in this 
way. The silver 
maps out the cells 
with unerring accu- 
racy, and encloses a 

FIG. 77. View obtained by changing focus of figure 76, showingUUCleilS ill Oach OlK\ 
villi ot intestine, etc. x 35. t .1 1 <- 

In the vessels from 




120 THE STUDENTS MANUAL OF HISTOLOGY, 

the pia mater, one frequently sees the termination of a capillary 
and commencement of an artery, by the appearance here and 
thereof a muscle cell coiled round the vessel. With a freezing 
microtome transverse sections of the different arteries and 
veins can be made from the fresh specimens. 

The silver method is recommended for the study of the 
endothelial layers of all vessels. 

For the intima, a section of the vessel is placed in a i per 
cent, solution of potassic bichromate for several days, then it 
can be pulled off with forceps, stained, examined, and mounted 
in glycerine. Chromic acid preparations are valuable here. 
For the further study of this layer consult the chapter on mus- 
cular tissue. 



CHAPTER IX. 



The Respiratory Passages. 

THE lungs first appear as an elevation on the anterior sur- 
face of the canal which becomes the oesophagus into which 
the elevation soon opens, forming a hollow sac. At its lower 
extremity a bifurcation appears, dividing the tube into two 




FIG. 78. Formation of the bronchial ramifications and of the pulmonary cells. A, B, 

development of the lungs, after Rathke. C, D, histological development of 

the lungs after J. Miiller. (Lcnget) 

branches. These branches divide again and again until the 
whole of the bronchial system is complete. Then the pulmo- 
nary vesicles are developed and last of all the trachea. 

THE LARYNX. 

The general surface of the larynx is covered with a layer 



122 THE STUDENTS MANUAL OF HISTOLOGY. 

of stratified epithelial cells, largely of the ciliated variety. Be- 
neath this is a layer of mucous membrane containing a net- 
work of capillaries. Between these two layers can occasionally 
be demonstrated a layer of connective-tissue cells. The 
nerves terminate in the mucosa in the form of terminal bulbs. 
The epiglottis is composed of a basis of reticular or elastic car- 
tilage and deep layers of epithelial cells cover its anterior sur- 
face, while the posterior surface has a much less covering of 
the same kind. 

THE TRACHEA, 

The trachea is a fibrous tube, composed of fifteen or 
twenty hyaline cartilaginous half-rings embedded in its anteri- 
or walls, together with all the layers present in the larynx. On 
its internal surface is a continuation of the ciliated cells of the 
larynx. Just beneath this layer is a thick basement membrane. 
External to this is the mucosa, and still more external a layer 
of loose connective tissue containing glands. A layer of 
striated muscle fibres stretches between the anterior surface of 
the ends of the incomplete cartilaginous rings. Between every 
two of these rings are strong bands of elastic and connec- 
tive tissue. 

THE BRONCHI. 

The bronchi have essentially the same structure as found 

in the trachea. Lining their tubes until they are reduced to 
5 \ of an inch in diameter are ciliated epithelial cells. As the 
passages become finer and finer by their division, the cartil- 
aginous half-rings disappear, and simple lamellae appear in 
their place. 

Smooth muscular fibres continue as rings round the 
bronchial tubes to near their points of termination. The walls 
trrow thinner and more delicate in structure ; and when the 
tube is reduced to -^ of an inch in diameter, pavement epi- 
thelium takes the place of the ciliated. This continues until 



THE STUDENTS MANUAL OF HISTOLOGY. 



123 



thelial cells. 



the branch is reduced so that it measures but -g 1 ^ of an inch, 
when it has only a basement layer of elastic fibrous tissue, lined 
with a thin mucous membrane covered with pavement epi- 
It is now known as the "ultimate bronchial tube/' 
It terminates in a pyramidal sac 
called the " pulmonary lobule," 
which when moderately extend- 
ed is about Jg- of an inch in 
diameter. It represents the 
lung of the frog in miniature. 




FIG. 79. Lobule of human lung, 
bronchial tube ; b, interior of lobule, 
tiary vesicles, x 15. 



ultimate 
:, pulmo- 



THE LUNGS. 

First of all then we must 
study the simple structure of 
the amphibian lung. The ani- 
mal is killed by breaking up 
the brain substance (pithing). 
The abdominal walls are 
opened in the median line with 
a pair of straight scissors. 
The under blade is then pushed 
up under the sternum, care be- 
ing exercised that it is kept in 
surface lest it wound the heart. 
The sternum is cut through in the median line, and just be- 
neath it lies the heart in its pericardial sac, uninjured and still 
beating. The mouth is opened, when a little papilla at its 
back part appears. This is the slit glottis of the frog, formed 
by folds of the mucous membrane of the mouth, in each fold 
of which is a cartilage of similar form, the arytenoid cartilages. 
Between these folds and in this slit place the end of a small 
blow-pipe, or what answers every purpose, a small glass pipette. 
If now air be forced through this tube the lungs will expand to 
their full capacity and rise out of and above the walls of the 



close apposition to the inner 



124 



THE STUDENTS MANUAL OF HISTOLOGY- 




FIG. 80. One-half frog s lung ; show- 
ing interior division into air cells. Natural 
size. 



opened thorax. An assistant now passes a thread tightly 
around the base of each lung and by aid of a pair of scissors 
both lungs are removed, inflated and uninjured. If placed 
near a warm stove, or in the sunlight, they soon dry and retain 

their expanded form for an indefi- 
nite time. When dry they can be 
opened and their internal arrange- 
ment examined even with the 
unaided eye. 

Each lung is a transparent oval 
sac, pointed at its posterior ex- 
tremity and covered with a layer 
of pleuro-peritoneal membrane. 
The internal surface is not smooth 
as in the salamander's, and the 
newt's, but is divided into a num- 
ber of smaller cavities formed by 
folds of the walls of the pulmonary sac. These folds divide 
the cavity into a number of " air cells," increasing the extent 
of surface and thus giving more room for the distribution of 
the branches of the pulmonary artery. Of such a structure is 
each pulmonary lobule, of the human lung. 

Each pulmonary lobule is divided into compartments by 
irregular partitions, on the walls of which the blood-vessels 
ramify. These compartments are known as the "pulmonary 
vesicles;" they correspond to the "air cells" of the frog's lung. 
Their average diameter is about jfo of an inch. It has been 
estimated that in the lungs of man there are eighteen hundred 
millions of them, exposing a surface of fourteen hundred 
square feet. The walls of the vesicles are composed of a thin 
connective tissue surrounded by elastic fibres. Unstriped 
muscle is absent from the greater part of the alveolar wall, ex- 
isting in small amount sometimes toward its base. The 
vesicles are lined with polyhedral cells, between which are 



THE STUDENTS' MANUAL OF HISTOLOGY. 1 25 

larger or smaller openings which lead into the lymph canalic- 
ular system (Klein). In the lungs is a rich, close net-work of 




FIG. 81. a, walls of alveolar duct. b, walls of alveoli, c, large flat nucleated cells 
lining alveoli. (Modified from Klein & Smith.) 

capillaries. The meshes are usually small, but vary according 
to the degree of distention of the vesicle. They are formed 
from the repeated divisions of the pulmonary artery and com- 
pletely encircle each individual vesicle ; giving rise in this con- 
nection to an uncommonly close net-work of tubes, which are 
but slightly embedded in the alveolar walls. The greater part 
of the walls of the blood-vessels extend into the central cavity, 
so that if the lung be but partly inflated, they will hang in loops 
in the lumen of the alveolus. 

METHODS OF EXAMINING. 

In order to study the lung tissue, portions of fresh lung 
may be teased or picked. Acetic acid or alkalies added, and 
examined at once. This shows readily the elastic fibres. The 
frog's lung may be inflated and dried as described above, and 



126 



THE STUDENTS MANUAL OF HISTOLOGY. 



thin sections made in every direction. The sections can be 
moistened, stained, and treated with the acetic acid when quite 




FIG. 82. Transverse section through the pulmonary substance of a child of nine months 
a, number of pulmonary cells, b, surrounded by the elastic fibrous net-work, which bound 
them in a trabecula-like manner, and, with the thin structureless membrane, forming their 
walls (a) ; d, portions of the capillary net-work with their vessels curved in a tendril-like 
manner, projecting into the cavities of the pulmonary cells, c, remains of the epithelium. 

(Frey.) 

satisfactory examinations can be made. If possible however, 
the blood-vessels and the air passages should be fully injected. 
It is in this way only that one gets anything like an intelli- 
gent view. In the smaller animals the venae cavae are tied, and 
the nozzle of the syringe secured in the right ventricle. The 
left ventricle is opened to allow the escape of the blood as it is 
forced out by the injecting material. At the same time the in- 
jecting mixture is flowing in the vessels the lungs are partially 
expanded by means of a blow-pipe in the trachea or bronchus. 
In a few moments the opening in the left ventricle is closed 
to prevent the escape of any of the injecting mixture. The 
color of the lungs will decide when they are sufficiently inject- 



THE STUDENTS MANUAL OF HISTOLOGY. 127 

ed. Prussian blue has afforded all that could be desired in our 
hands. Then very small pieces of the injected lung are 
placed in melted cocoa-butter and allowed to remain there for 
two or three hours, when they are removed and the butter 
allowed to harden. Thin sections can be made with a razor in 
every direction, with or without the aid of the microtome. 
Instead of inflating the lungs with air,melted cocoa-butter may 
be used. Oil of cloves dissolves out the butter in a short time, 
when alcohol can be added to get rid of the oil. The specimens 
can be stained now with carmine or logwood, cleared in oil, and 
mounted in dammar. These organs may be hardened by in- 
jecting in the trachea, or one of the bronchi, a weak solution 
of chromic acid, ^ per cent. 

Enough should be injected to distend the lungs slightly, 
when the trachea or bronchus should be tied and the whole 
lung placed at once into some of the same solution. The 
lungs must be cut in small pieces in a few days and placed in 
a fresh solution, either of the same strength or slightly in- 
creased. In a week or ten days the pieces are transferred to 
dilute alcohol and in a few hours to spirits of full strength. 
Sections can be made now, stained, cleared and mounted. 
The lungs of embryos should be studied especially. Simple 
hardening in alcohol, staining and clearing, will be sufficient to 
enable one to recognize the structure of the whole organ. 

Pigmented lungs or portions of lung are not uncommon. 
A fine, black, granular pigment is observed in the walls of the 
alveoli. This may be caused by small effusions from the pul- 
monary capillaries ; yet it is almost invariably of extraneous 
origin, being composed of minute particles of carbon inhaled 
in the smoke and soot. The lungs of those employed in coal 
mines are made sometimes quite black by their inhaling par- 
ticles of carbon in a finely divided state. Some of these par- 
ticles may enter the lymphatics and be carried to the lymph 
glands of the bronchi, or to more distant structures. Animals 



128 THE STUDENTS' MANUAL OF HISTOLOGY. 

confined in a sooty room suffer this same pigmentation of their 
lungs. 

If it is desired to examine lung tissue after it has under- 
gone some of the progressive inflammations, small pieces 
should be hardened in chromic acid or Mailer's fluid and sec- 
tions carefully made at the proper time. 

In suspected cases of phthisis where it is very desirable 
to know the progress made by the disease, great aid may be 
procured many times by an examination of the sputa of the 
patient. It is now a recognized fact that phthisis has been 
diagnosed and is diagnosed in this way, weeks, months before 
other signs are manifest. 

As expected ingredients in the sputa, one finds remains of 
food, starch granules, epithelium, air bubbles, mucous cells, pus 
cells, blood corpuscles, large granular cells, and perhaps, pig- 
ment cells. If now besides these there are found fragments of 
lung tissue, as yellow elastic fibres, it shows that there must be 
a disintegration of the pulmonary tissue, a condition which 
must denote serious trouble. If these fibres are not found it 
does not by any means prove that serious trouble may not exist, 
but their presence is very significant. Some special directions 
should be given to the patient whose sputa we are about to 
collect. First, the mouth should be carefully and thoroughly 
rinsed and teeth brushed after each meal. Second, the vessel 
in which the sputa are collected should be scrupulously clean. 
Third, if the patient is in the habit of using tobacco, it should 
be denied during the collection of the sputa, as the fibres of 
the leaf might mislead and cause a wrong diagnosis. If the 
amount of sputa is small, then all raised during the twenty- 
four hours should be saved. If large, that first raised in the 
morning should be preferred. 

Any little grayish masses should be chosen and placed at 
once under the microscope. Acetic acid will clear up the 
mucous, etc., and render more distinct the yellow fibres if they 



THE STUDENTS' MANUAL OF HISTOLOGY. 



129 



are present. If this examination reveals nothing, the following 
method should be adopted : 

Make a solution of sodic hydrate, 20 grains to the ounce 




FIG. 83. Fragments of lung tissue (yellow elastic fibres). Sputa from case of phthisis. 
Mucus, pus, epithelium, granular matter, etc., were in great abundance, x 215. 

of water. Mix the sputa with an equal bulk of this solution 
and boil. Then add to this mixture 4 or 5 times its bulk of 
cold water. If possible, pour into a conical-shaped glass and 
set aside. Soon the yellow fibres, if present, will fall to the 
bottom ; from here they can be drawn, up with a pipette and 
examined. Several glass slides should be examined at a 
single sitting, and the examination should be repeated every 
few days until the presence or absence of these fibres is 
satisfactorily demonstrated, 



CHAPTER X. 



The Salivary Glands and the Pancreas. 

THE salivary glands all resemble each other in general 
structure, although minor differences exist. The differ- 
ence in the secretions of the different glands depends upon 
a slight difference in their anatomical structure. 

In all the glands the gland tissue is divided by connective- 
tissue septa into lobes and lobules. The connective-tissue 
frame-work surrounds the ducts and gives support to the 
blood-vessels, nerves, etc. 

The largest (microscopical) ducts are lined with a single 
layer of columnar epithelial cells. In their walls are non- 
striated muscle cells. In the smaller ducts there is a relative- 
ly small lumen lined with columnar epithelial cells which are 
composed of closely arranged, thick, longitudinal rods (Kol- 
liker.) These rods anastomose laterally to make the intra- 
cellular net-work of Klein. The small ducts branch into still 
smaller ones which ultimately terminate in the alveoli of the 
gland substance. 

Just before the duct terminates it becomes narrower, 
sometimes branched, its lumen smaller, and its epithelial cells 
become a single layer of flattened cells. 

The terminal alveolus is a rounded sac, convoluted and 
wavy in appearance. These extend in every direction. They 
average about the -^ of an inch in diameter. These follicles 

130 



THE STUDENTS MANUAL OF HISTOLOGY. 



*3* 



or alveoli represent the rounded sac-like terminations of the 
salivary tubes. Between these are blood-vessels, capillaries, 
nerves, lymphatics, and connective tissue. 

In the parotid gland — the only true salivary gland — and 
in most of the lobules of the submaxillary, the lumen of the 
alveoli is small and lined with a single layer of glandular epi- 
thelial cells, which are columnar in shape but very short. 
During secretion the lumen is smaller and the lining cells are 
broader. In a few of the lobules of the submaxillary and in 




FIG. 84. Two salivary tubes from the lobule of a muciparous gland, entering the main duct, 
a, duct of the lobule, b, salivary tube, c, follicles, on one side, as they appear in situ. 
d, follicles separated from each other, showing the windings and offshoots of the salivary tube. 

(Kolliker.) 

nearly, if not all of those of the sublingual the alveoli are 
larger and lined with two kinds of cells. 1, The mucous 
cells are like the goblet cells already described. These con- 
tain a transparent substance called mucigen (Heidenhain), 
which during the secretion of the gland is transformed into 
mucin. 2. The crescents of Gianuzzi. These are composed 
of nucleated, polyhedral, granular cells, smaller than the 
mucous cells and situated in the periphery of the follicle. They 
are arranged very close together after the fashion of a crescent. 
They represent young mucous cells. After exhaustion of a 
gland, after the mucous cells have given off their mucin, they 
disappear, and now only a granular substance remains in the 
body of the cell. The alveoli are surrounded by a fine capil- 
lary net-work of blood-vessels and lymphatics. 



3 2 



THE STUDENTS MANUAL OF HISTOLOGY. 



A net-work of fine nerves is seen in connection with the 



intra-lobular connective tissue. 




In this net-work are numerous 
ganglia composed gener- 
ally of unipolar ganglion 
cells. The fine nerve 
branches terminate in the 
epithelial cells lining the 
salivary tubes, each cell 
representing the terminal 
organ of each nerve fibre. 

METHODS OF EXAMINING. 

Small pieces of the 
gland are placed in a 
saturated solution of pic 
ric acid for 48 hours. 
Sections can then be made 
with a freezing micro- 
tome. 

Heidenhain employs 
absolute alcohol and stains with carmine. Small pieces can 
be macerated in, at first, a weak solution of chromic acid -^ 
grain to the ounce of water, and gradually increased to % 
grain to the ounce. The ducts are best injected with the 
Prussian blue. 

Osmic acid affords a useful reagent, especially for the 
study of the epithelial cells. A .5 per cent, solution should be 
employed, and small pieces of the tissue allowed to remain in 
it for 48 hours. If this reagent is used for hardening, a 
weaker solution (.25 per cent.) should be used, and the tissue 
allowed to remain in it for 2 or 3 days, when sections can be 
made with the freezing microtome. 

THE PANCREAS. 

The pancreas was formerly known as the "abdominal 



FIG. 85. The subm<u =7 g.and of the dog. a, 
mucous cells. b. protoplasma cells. c, crescent. 
d : transverse section of an excretory duct, with the 
peculiar cylindrical epitneiium. (After Heidenhain.; 



THE STUDENTS MANUAL OF HISTOLOGY. 1 33 

salivary gland." It is divided into lobes and lobules and in 
its intimate structure resembles the salivary glands. The tis- 
sue is some softer than that belonging to these glands ; this is 
simply because the lobes are not so compactly arranged. The 
cells in the alveoli resemble those of the parotid. 



CHAPTER XI. 



The Pharynx. GEsophagus. Stomach and 
Intestine. 

THE PHARYNX. 

THE walls of the pharynx are composed of transversely- 
striated muscles with fibrous connective tissue. They are 
lined by a mucous membrane which is covered with a layer of 
epithelial cells, columnar and ciliated in the upper third, but 
squamous and destitute of cilia below. The mucous mem- 
brane is rich in mucous glands which, in the upper part, collect 
in groups with a common excretory duct. 

THE OESOPHAGUS. 

At about the commencement of the oesophagus (cricoid 
cartilage) the striated muscle walls of the pharynx are re- 
placed by the smooth muscle tissue until very soon there are 
two muscular layers, an external longitudinal, and an internal 
circular. This arrangement of muscle extends throughout the 
remainder of the alimentary canal. Beneath the internal cir- 
cular layer is a coat of submucous areolar tissue, in which are 
the glands opening on the surface of the mucous membrane. 
The mucous membrane is quite thick and is arranged in longi- 
tudinal folds when the oesophagus is not distended. It pro- 
jects into the epithelial layer as small cylindrical papillae, in 
the centre of which may be a lymphatic, terminating in a loop 
or in a single blind vessel. A thick layer of flattened epi- 
thelium covers the membrane and extends to the cardiac 

i34 



THE STUDENTS MANUAL OF HISTOLOGY. 



135 



orifice of the stomach. Between the mucous and submucous 
coats is a longitudinal layer of smooth muscle fibres, which 
forms a continuous coat at the lower part of this tube. This 
is the muscularis mucosae. 



/WYAyn 




THE STOMACH. 

The stomach is surrounded by 
a serous coat derived from 
the peritoneum, beneath which 
is a smooth muscular layer, 
continued directly from the oeso- 
phagus and arranged the same as 
described for that tube. Still deep- 
er than this is another layer of musr 
cular tissue arranged in an oblique 
manner. Between the muscular 
and mucous coats is a quantity of 
areolar tissue in which are found 

FIG. 86. Vertical section of the hu- , hlnnH vp«p1c fat rHk HT 

man gastric mucous membrane ; a, sur- me U1UUU - VCbbClb, ld.L CCllh, CIC. 
fece papillae, b, glands. (Frey.) ^ mucous mem brane is at Once 

very complex and very inter- 
esting. It is loosely attached 
to the muscular coat and is 
easily movable over it ; so 
that when the stomach is 
empty it is thrown into 
numerous folds, 1 or rugae, which 
have a general longitudinal di- 
rection, and are most marked 
along the great curvature. 
They are entirely obliterated 
when the organ is distended. 
Lining the mucous membrane 
over the whole surface of the 
stomach is a layer of columnar 




FIG. 87. Horizontal section through fundus 
of stomach of dog. The peptic glands are cut 
transversely, a, cells lining lumen cf gland, b, 
parietal cells, (after Klein »nd Smith.) x 
400 



136 



THE STUDENTS MANUAL OF HISTOLOGY 



cells -gfo to 3-^p- of an inch high, and ^^ to -^^ of an inch 
broad. Among these cylindrical cells are a few that are gob- 
let-shaped; especially is this true during digestion when many 
of these cells are seen. The epithelium extends into the ducts 
of the glands which are placed perpendicularly to the surface. 
Beneath the layer of epithelium is a basement membrane of 
flat nucleated endothelial cells. In the mucous membrane 

are found connective-tissue 
cells, endothelial cells, lymph 
cells and the glands and their 
tubes. If the surface of this 
membrane be examined with 
the aid cf a common lens small 
depressions are seen about the 
■j^q of an inch across. On 
these alveoli are the small round 
openings of the ducts of the 
tubular glands. Two kinds of 
glands are imbedded in . the 
mucous membrane; those in the 
pyloric portion — pyloric glands, 
and those in the other portions, 
— peptic glands. 

The peptic glands consist of 
three or four gland tubes, 
closed at their deep extremity, 
which empty into one common 

FIG. 88. Peptic gland from cardiac portion duct. A gland is divided into 

of human stomach. 1, Excretory tube, lead ng . 

to the surface. 2, Tubular follicles, containing three parts, ltS duct, neCK and 

spheroidal cells. [Kolliker.) , 

body. The duct extends from 
\ to -J the whole length of the tube; the neck from J- to % of 
the same distance. Both the duct and neck are lined with the 
same cells that cover the free surface of the mucous membrane, 
with this difference, that in the neck the cells are shorter and 




THE STUDENTS' MANUAL OF HISTOLOGY. 



137 



the nuclei smaller. Outside of these cells, but inside the walls 
of the tube, are other nucleated cells of a granular appearance. 
They do not form a continuous layer, being found only here 
and there. For a long time they were described as " peptic 
cells," but Heidenhain showed their position in the tube, and 
gave them the name of " parietal cells." 

The body of the gland is lined with a layer of cells directly 
continuous with those of the neck, only here the cells are more 
columnar. They have a spherical or oval nucleus which takes 
staining very readily. But few parietal cells are seen in the 
body of the gland, and they decrease very rapidly towards the 
fundus (Rollet.) During digestion the cells in the body of the 
glands become thicker, more opaque and granular, giving the 
whole gland a broader appearance (Heidenhain.) 

As these glands approach the 
pyloric portion of the stomach, 
the ducts become longer and 
the remaining portions shorter. 
It has been noticed in some 
animals that when the peptic 
and pyloric glands meet, they 
not only intermix, but also that 
the peptic glands become trans- 
formed into the pyloric. 

The pyloric glands have a 
much longer duct, with a very 
short neck. The body is com- 
posed of two or more tubes. The lumen of the gland is 
many times larger than in the other glands. No parietal cells 
are found in these glands. By some they are regarded as 
simple peptic glands, while this is denied by others; they are 
certainly not mucous glands as was formerly supposed. 

These glands continue to the pyloric orifice, and then pass 
through into the duodenum as Brunner's glands, which are 




FIG. 89. Fundus of a gland tube. The chief 
•cells a, have a distinct reticulum, b, the nu- 
cleated parietal cells. c, lumen of tube. 
[After Klein.] x 450. 



138 THE -STUDENTS' MANUAL OF HISTOLOGY. 



identical with them in structure. A layer of muscle fibres 
separates the mucous from the submucous tissue (musculrisa 
mucosae.) 

The fine terminal arterial branches enter the mucous mem- 
brane and form a plexus upon the walls of the gland; branches 
of this plexus surround the mouths of the glands and borders 
of the alveoli; (see figure 72.) The lymphatics arise in the 
mucous membrane by a net-work of vessels, situated between 
the tubules. They are not as superficial as the blood-vessels, 
and they commence as loops, or in dilated extremities. Be- 
neath the mucous membrane they empty into a fine plexus, 
then pierce the muscularis mucosae to form another coarser 
plexus in the submucous coat; the branches then penetrate the 
muscular layers and follow the direction of the blood-vessels 
until they reach some of the lymphatic glands found on the 
surface of the stomach. 

Fine nerve gangliated plexuses are seen between the mus- 
cular layers and in the submucous coat. 

THE INTESTINE. 

The walls of the intestine, both small and large, are the 
same as those of the oesophagus and stomach, viz.: 1, an epi- 
thelial layer resting on 2, a mucous membrane beneath which 
is 3, the muscularis mucosae which in turn is surrounded by 
4, a submucous tissue, and external to this are 5, the circular, 
and 6, the longitudinal layers of muscle cells. A serous 
covering, from the peritoneum, surrounds the whole. 

THE SMALL INTESTINE. 

The mucous membrane of the small intestine is thrown 
into a number of folds which cannot be obliterated by the dis- 
tention of the canal. These are the valvulae conniventes. 
They extend one-half or two-thirds of the distance around the 
canal, are about x /z of an inch wide and are placed in close 



THE STUDENTS MANUAL OF HISTOLOGY. 



1 39 




succession. Small processes of the mucous membrane cover 
these folds completely, and fill the spaces between them. These 
prolongations are the villi; they are from ^ to -^ of an inch 

long, and are most 
numerous in the duo- 
denum and jejunum: 
Krause estimates the 
whole number in the 
intestine to be at least 
four millions. Colum- 
nar epithelial cells 
cover the villi and the 
mucous membrane of 
the small intestine 
throughout its entire 
length. At the base 
of each villus is a small 
arterial branch which 
runs in the centre toward the surface. It soon gives off a 
number of branches to make a most beautiful capillary net- 
work which terminates in a vein, and this in turn penetrates the 
mucous coat to pass into the submucous layer (see figure 73.) 
The small lymphaticor lacteal, occupies the centre of the vil- 
lus, usually as a single tube, sometimes double, with walls of a 
single layer of endothelial cells or plates. It usually com- 
mences as a blind tube, with perhaps a dilated extremity and 
surrounding it are a few muscle cells arranged in a longitudinal 
manner. These cells are prolongations from the muscularis 
mucosae and when stimulated they cause a decided retraction 
of the villus. 

The matrix of each villus is composed of a delicate retic- 
ulum in which are seen a few nucleated fat cells. This retic- 
ulum forms the interstitial substance of the basement mem- 
brane, between the covering of epithelial cells and the mucous 



FIG. 90. Transverse section of the ileum of an infant, 
injected. a, blood-vessels filled with the injecting ma- 
terial, b, muscle walls, c, vi lli. 



140 



THE STUDENTS MANUAL OF HISTOLOGY. 



membrane; from this, prolongations extend between the 
epithelial cells on the surfaces of the villi; it forms the inter- 
stitial substance between the endothelial plates composing the 
wall of the lymph capillaries, and also of the blood capillaries. 




FIG. 91 . Vertical section of a villus of the small intestine of a cat, hardened in chromic 
■acid, a, streaked basal border of epithelium, b, cylindrical epithelium, c, goblet cells, d, 
central lymph vessel, e, smooth muscular fibres which lie nearest to the lymph vessels, f, ade- 
noid stroma of the villus in which lymph corpuscles lie. (Klein.; 

A very interesting question presents itself here as to the man- 
ner in which chyle passes from the interior of the intestine 
Into the lacteals and blood-vessels. It is quite generally taught 
that the minute chyle globules pass directly into the body of 
the cells covering the villi, and thence pass into the capillaries 
or lymph ducts. Thus Kolliker and others have described 
and illustrated these particles of oil as passing through the 
cells. The researches of Dr. Watney, under the direction of 
E. Klein, have thrown much needed light upon this subject. 
According to these authorities the epithelial cells are engaged 
here in secreting mucus and not in absorption. Absorption 



THE STUDENTS MANUAL OF HISTOLOGY. 



i4r 



takes place through the interstitial substance of this delicate 
reticulum. The chyle globules then pursue the following 
course: They enter the interstitial substance between the 
epithelial cells and pass into the directly continuous basement 
membrane; from here they pass into the matrix reticulum of 
the villus, and finally into the interstitial substance between the 
endothelial plates into the blood or lymph channels. 

Thus it is seen that there is a continuous lymph-canalicu- 
lar system from the free border of the villus to the central 
vessels. This affords a very satisfactory explanation of the 
absorption from this canal, for, owing to the centripetal direc- 
tion of the flow in the lymphatic vessels, there must be a strong" 

tendency for matter out- 
side the vessels to pass 
into their interior. At 
the base of the villi are 
the crypts of Lieber- 
kiihn. These are minute 
tubes placed perpendi- 
cularly to the surface, and 
consist of tubes lined with 
columnar epithelium. 
They are from ^ to 3^ 
of an inch in length and 
■^J-g- of an inch broad. In 
the submucous tissue of the duodenum are the glands of 
Brunner, identical with the pyloric glands. 

Between the longitudinal and circular layers of muscle is 
a plexus of band-like nerve branches, among which are 
groups of glanglion cells, called the " plexus mesentericus of 
Auerbach." Branches pass from this plexus into the sub- 
mucous tissue to give rise to the "plexus of Meissner." 
Here are unipolar, bipolar, and multipolar ganglion cells. 




FIG. 92. Lieberkiihnian glands (a) of the cat, with 
the intestinal villi (b) situated over them. (Kolliker.) 



I42 THE STUDENTS MANUAL OF HISTOLOGY. 

Branches are distributed from both these plexuses in every 
direction. 

THE LARGE INTESTINE. 

The walls of the large intestine resemble in all respects 
those of the small. The mucous membrane, however, is 
destitute of villi, but more freely supplied with the crypts 
of Lieberklihn. Here these glands are placed more closely 
together, are longer and more numerous. 

METHODS OF EXAMINING. 

There are many methods employed to demonstrate the 
structure of these organs. Only stomachs from recently 
killed animals should be chosen, for if only a short time 
has elapsed since the death of the animal, the softer struct- 
ures of the inner coats will be affected. 

A piece of stomach an inch square, or several such 
pieces are placed in Muller's fluid, to be transferred in a week 
or ten days to alcohol. Vertical sections show all the coats 
to good advantage. Small pieces can be hardened in al- 
cohol alone, and stained with carmine. Sections should be 
made perpendicular to the free surface of the mucous mem- 
brane, in order to obtain good views of the glands. For 
this purpose, small pieces from different parts of the mucous 
membrane are placed immediately in absolute alcohol. When 
hardened, vertical sections are made as thin as possible, and 
stained in carmine or haematoxylin. The sections are well 
preserved in glycerine or dammar. Horizontal sections show 
the different parts of the glands cut across. They are to be 
stained and mounted as the others. Small pieces of the 
mucous membrane are placed in a % per cent, solution of 
osmic acid for 24 hours and sections made with the freez- 
ing microtome. This process demonstrates the cells in the 
glands in a very satisfactory manner. 



THE STUDENTS MANUAL OF HISTOLOGY. 143 



To study the blood-vessels of the organ, the entire animal, 
if small, should be injected. Beautiful preparations are made 
from the stomach of a cat or rabbit, injected with Prussian 
blue or carmine. 

Pieces of the small intestine are treated like those of the 
stomach, only in the injected specimens sections should be made 
with the aid of a freezing microtome in order that the villi may 
not be injured. Such specimens should be stained but slightly. 
To examine the lacteals, the animal should be given a meal 
composed largely of fatty matters, and then killed in 3 or 4 
hours. Small pieces of the mucous membrane are placed in a 
1 per cent, solution of osmic acid and allowed to remain therein 
nearly 48 hours. This stains all the fatty particles black, and 
thus shows the outlines of the lacteal in the centre of the villus. 
Chromic acid, chromate of potash, teasing, penciling, and 
tingeing should not be forgotten 



CHAPTER XII. 



The Liver. 

THE liver is very early to show itself, for it has attained 
comparatively an enormous size by the end of the first 
month of uterine life. Buds or projections appear on either 
side of the intestine to form the two principal lobes of the 
liver. It soon occupies nearly the whole of the abdominal 
cavity and in proportion to the body weight, bears the fol- 
lowing relation according to Berlach: 

At the end of the first month as i to 3. At full term as 1 
to 18. In the adult as 1 to 36. It is very soft in structure 
during the first months, but as its development progresses its 
tissue becomes more firm. The liver is very peculiar in its 
structure, and is unlike any of the other glands of the body. 

By the unaided eye one is just able to discern on the 
natural external surface of the human liver an innumerable 
number of pentagonal or hexagonal islets, known as the 
hepatic lobules. They are about -f Y of an inch in diameter 
and their number corresponds with the number of central 
veins. In the liver of the pig these lobules are easily dis- 
tinguished by the naked eye, for a considerable amount of 
connective tissue completely separates them from one another. 
In the human liver this connective tissue is not nearly so well 
developed, and in many parts of the organ the surface of one 
lobule is in direct contact with the adjacent ones. 

Each lobule is composed essentially of two substances : 
144 



THE STUDENT S MANUAL OF HISTOLOGY. 



45 



the liver cells and the capillaries. The capillaries present an 
uncommonly complicated net-work. Commencing with the 
portal vein, it is seen to enter the transverse fissure together 




FIG. 93. Transverse section of a single hepat'c lobule. (Sappey.1 1 , intralobular vein, 
cut across. 2, 2, 2, 2, afferent branches of the intralobular vein. 3, 3, 3, 3, 3, 3, 3, 3, 
branches of the portal vein, with its capillary branches, forming the lobular plexus, extend- 
ing to the intralobu lar vein. 

with the hepatic artery, hepatic duct, nerves and lymphatics, 
surrounded and bound together by a fibrous connective tissue, 
the capsule of Glisson. From the portal vein are given off 
small branches which pass between adjacent lobules. As 
these terminal branches extend only between the lobules and 
never enter within them, they are called the intermediate 
veins, interlobular veins. From these veins branches are de- 
rived, which rapidly divide into a close capillary net-work, and 
approach the centre of the lobule in a radial manner. The 
net-work is formed by horizontal or transverse branches con- 
necting the principal capillaries as they pass from the periph- 
ery to the centre of the lobule. This forms a "lobular plexus" 
of capillaries, with each vessel about the -g-gVir of an inch in 



I46 THE STUDENTS' MANUAL OF HISTOLOGY. 



diameter. As they near the centre of the lobule, they unite 
together to form veins of considerable size, which empty into 
a single central vessel placed in the long axis of the lobule. 
This vessel, from its central position, is called the intralobular 
vein. It is from the 10 1 00 to the ^-J-g- of an inch in diameter 
and empties into a larger vessel just at the base of the lobule, 
from its position, named the sublobular vein. These veins 
collect the blood from all parts of the liver, and convey it to 
larger vessels, which become larger still, until the three hepatic 
veins are formed. At the termination, then, of the portal vein, 

are the interlobular branches, and 
the intralobular vessels mark the 
commencement of the hepatic 
veins, the lobular plexus being the 
intermediate system of capillaries. 
The hepatic veins have very thin 
walls, much thinner than the por- 
tal, and they are not surrounded 
by any Glisson's capsule, but are 
quite firmly united to the hepatic 
tissue. The hepatic artery enters 
fig. 94. a, smarr hepatic vein, b, sub- the sheath at the transverse 

iobular veins, c, lobules. (Kiernan.) /. , . .. . , rr 

fissure, and immediately gives off 
branches to the walls of the portal vein, and a very rich plexus 
to the walls of the hepatic duct, so that when this artery is 
thoroughly injected it almost covers, with its capillaries, the 
walls of the duct. It supplies also the capsule of Glisson, the 
branches known as capsular branches. 

Branches of this artery are interlobular, and accompany 
the branches of the portal vein. According to Beale, these 
branches lead into special veins, which accompany the arteries 
in couples, and join the interlobular branches of the portal. 
According to some observers, the capillaries and veins from 
the hepatio artery join the capillaries of the lobules by an 




THE STUDENTS' MANUAL OF HISTOLOGY. 



147 




FIG. 95. Liver cells, 
rig fat. x 400. 



anastomosis of the blood-capillaries of the bile ducts with the 
capillaries of the lobules. 

All the space not occupied by the capillary net-work is 
filled with the glandular cells of the 
organ. These are circular when 
seen single, but angular, pentagonal, 
or hexagonal when viewed in thin 
sections of the liver. They are about 
the yoVo °f an mcn m diameter, and 
are provided with a well marked 
nucleus. Here again is the inter- 
cellular and intranuclear fibrillar 
net-work of Klein and others. Some 
of the cells have two nuclei, and 
minute fat globules, one or more to 
to each cell are very generally seen. The fatty embedments 
are present in the liver cells of adults whose diet is rich, and 
they occur also in the young infant, and in the fattened lower 
animals. The liver cells may become in this way crowded 
with fat, which soon dissappears when the manner of living is 
changed. Small particles of pigmentary matter are sometimes 
abundant in the cells, giving them a peculiar brownish appear- 
ance. Each cell is in direct contact by some of its surface with 
a blood-vessel. 

It is with the greatest difficulty that the bile capil- 
laries can be investigated. A fine system of bile ducts is 
recognized running with the interlobular branches of the por- 
tal vein. Into these fine branches empties a delicate net-work 
of the finest biliary capillaries, their diameter varying from the 
2 s 1 6 to the yg-J-tf-ff- of an inch. These capillaries run between 
the liver cells, and thus enclose polygonal spaces of the shape 
and diameter of a single cell. In this way every liver cell, 
from the periphery to the centre of the lobule, is in contact, by 
one part or another of its surface, with these fine biliary pass- 



48 



THE STUDENTS MANUAL OF HISTOLOGY. 



ages. These capillaries always pursue a course with reference 
to their keeping, as far as possible, from the blood capillaries, 
for there always remains part of a cell between the bile capil- 




FlG, 96. Biliary capillary of the rabbit's liver. 1. A part of the lobule; a.vena hepatica, 
b, branch of the portal vein, c, biliary ducts, d, capilliaries. 2. The biliary capillaries (b) 
in their relation to the capillary blood-vessels (a). 3. The relation of the biliary capillaries 
to the hepatic cells, a, capillaries, b, hepatic cells, c, biliary ducts, d, capillary blood- 
vessels (after Frey.) 

lary and blood capillary. These biliary canals pass between 
the boundary surfaces of two neighboring cells, and not simply 
along their borders; in this way the surface of a cell may be 
divided into two equal or unequal parts. Whenever a bile duct 
is found along the border of a cell, it will be noticed that no 
blood capillary comes in contact with that part of the cell in 
any way. It is impossible, then, to find a fine bile passage and 
a blood capillary without intervening cell substance, and more 
than this, if a few cells exist in the liver not touched by blood- 
vessels, they are sure to come in contact with a fine gall duct. 
Authorities are about equally divided on the question of 
the bile capillaries having a membrana propria. Some hold 
that the liver cells themselves form the walls of the ducts, while 
others describe and illustrate these finest ducts as possessing a 



THE STUDENTS MANUAL OF HISTOLOGY. 



149 



very tenacious, but delicate membrane. The latter view, we 
believe, is the correct one. 




FIG. 97. From investigations of H. R. Stiles on the Texas cattle disease, a, bile capillaries, 
b, liver cells, c, membrana propria of the bile capillary. 

METHODS OF EXAMINING. 

The usual methods are followed in studying this organ, 
viz.: Injecting, hardening and staining. To examine the unin- 
fected liver, small pieces are placed 
at once in Miiller's fluid and al- 
lowed to remain there for two 
weeks, at least. A large amount of 
the fluid should be used. The 
pieces are then placed in dilute al- 
cohol for a day or two, and then in 
alcohol of full strength for two or three days longer. Sections 
can be made now without trouble, and stained with hematoxy- 
lin. Sections should be made in at least two directions: 




FIG. 98. From Quarterly Jour. Med. 
Science (Hayes) 1879, July, by W. G. 
Davis. a, liver cells. b, bile capillary, 
having a membrane. 



150 THE STUDENTS MANUAL OF HISTOLOGY. 

First, parallel to the surface, in order to cut the intralobular 
veins across, and show the arrangement of the lobular plexus 
of capillaries and their relation to the liver cells. Second, ver- 
tical to this surface, showing the intralobular veins along their 
length, and their terminations in the sublobular vein. These 
vessels are seen to much better advantage in injected speci- 
mens. The liver of the rabbit or cat is especially suitable for 
injection. The animal should be killed by bleeding. A 
branch of the artery, or portal or hepatic vein, or branch of a 
duct may be injected, or several of these may be injected at 
the same time with different colored mixtures. As in the case 
of many of the vessels of the different organs, so here especi- 
ally will it be wise to make a slit through the walls of the 
vessel in a longitudinal direction, and insert the pipe into this 
rather than into the opening of the cut end of a vessel. In this 
way a pipe can be inserted into a vessel scarcely larger 
than the pipe itself. To inject the portal vein thoroughly, 
first a solution of salt should be injected in order to wash out 
the blood. 

To inject the biliary passages, the pipe of the injecting 
apparatus is secured in the common bile duct, and slight 
pressure employed. The Prussian blue mixture is satisfac- 
tory here, and as soon as a few of the lobules are seen colored 
by the blue, the duct should be tied, and that part of the 
organ placed in Miiller's fluid, afterwards in spirits, and finally 
stained slightly with hematoxylin, cleared in oil of cloves, 
and mounted in dammar. 



CHAPTER XIII. 



Kidney. 

THE first trace of a urinary apparatus is found at an early 
period of embryonic life, and consists of two organs known 
as the Wolffian bodies; these are fully developed by the end of 
the first month and hardly to be detected after the second. 

At this early period the alimen- 
tary canal is a blind tube from which 
is given off a diverticulum. From 
this canal three diverticula arise. 
From the anterior one will be de- 
veloped the female generative organs 
— uterus, fallopian tubes, and the 
analogous organs in the male — 
prostatic vesicle and appendage to 
epididymis. From the posterior one 
will be developed the kidneys of the 
adult. Between these two will arise 
the Wolffian bodies. 

When fully developed, they will 
correspond in structure to the true 
kidney ; the tubules however will be 
about four times as large. The 
physiology of these bodies is not un- 
derstood, but it is altogether probable that they answer the 
same purpose in the embryo that the kidneys do in the adult, 
viz.: They throw off from the body some principle that would 
be injurious to it if retained. 

151 




FIG. 99. Diagrann of the forma- 
tion of the uro-genital organs. 1. 

a, intestinal canal with protuberance 

b. 2, The protuberance is very 
much developed, a, allantois. b, 
the urachus. c, the bladder, d, 
the genito-urinary sinus, with three 
protuberances. 1. duct of Miiller. 
2. Wolffian body. 3, the kidney. 
(after Kiiss.) 



152 



THE STUDENTS MANUAL OF HISTOLOGY. 



At this early history in the life of the embryo, the Wolffian 
bodies, liver, and intestine fill the abdominal cavity, and they 
are the only organs of any size present. After the first month 
these bodies commence to diminish in size while the organs be- 
hind them as rapidly increase in size. The result of this is, 
that at the end of the second month the order has been re- 
versed, and now the true kidneys rise from behind the tem- 
porary or false ones, and by their rapid growth leave the 
atrophied Wolffian bodies at their lower parts. 




FIG. 100. Vertical section of the kidney. (Sappey.) I, i , 2, 2, 3, 
3, 3, 4, 4, 4, 4, pyramids of Malpighi. 5, 5, 5, 5, 5, 5, apices of the 
pyramids surrounded by the calices. 6, 6, columns of Bertin. 7, pelvis 
of the kidney. 8, upper extremity of the ureter. 

The kidney of the adult is likened to a bean in shape; the 
concavity of the bean representing the hilum of the kidney. 



THE STUDENTS MANUAL OF HISTOLOGY. 



153 



At this place the ureter receives the urine, and the blood-ves- 
sels find their entrance and exit. 

A vertical section through this organ, from its convex to 
its concave borders reveals from twelve to twenty eminences 
projecting into the pelvis ; these are the papillae. On each 
papilla there are from twelve to twenty openings which rep- 
resent the terminations of that number of collecting tubes. 

The unaided eye readily discerns a difference in structure 
between the part of the organ lying towards its concavity and 
the part towards its convexity. The part toward the papillae 
has a fibrous parallel arrangement, while the other part is 
darker, homogeneous, or granular in appearance. The former 
is the medullary and the latter the cortical substance of this 
organ, The medullary substance can be 

divided into pyramids; each pyramid 
having a papilla for its apex and 
an imaginary line between the 
medullary and cortical portions for 
its base. If one of the twelve or 
twenty tubes forming each papilla be 
examined, it will be seen to divide 
into two or more branches, each of 
these branches dividing again 
until they are reduced in size 
to about the yi-^ of an inch. This 
process of division is generally corn- 
Diagram illustrating the j t b the time t h e tubes are one- 

d cortical pyramids, a, 1 J 

fourth of an inch from the papilla; 




FIG. 101 
medullary and cortical pyr 
papilla, b, external cortical layer, c, 
boundary line between the medullary, 

and cortical substances, d, straight the tubes then proceed in a straight 

border of the 



urinilerous tubes, e, medullary rays. 



course to the extreme 
cortical substance, unchanged in their diameter. These canals 
are collected into bundles, and as they are removed from 
the papilla, the bundles become separated from each other: as a 
result of this, there is a long, narrow pyramid between them and 



i54 



THE STUDENTS MANUAL OF HiSTOLOGV, 



the cortical pyramid. The base of this pyramid is formed by 
cortical layer, the sides are bounded by the 
straight canals and the apex 
extends past the dividing line 
into the medullary pyramid. 
The straight canals that are 





FIG. 103. Glomeiulus of the rabbit (dia- 
gramatic.) a, vas afferens. b, vas efferens. c, 
glomerulus, d, under portion of the capsule- 
( without epithelium), e, neck, f, epithelium of 
the glomerulus; and g, that of the inner surface 
of the capsule after treatment with silver. (From 
Frey.) 

known in the medullary por- 
tion as the tubuli uriniferi recti 
are known in the cortical por- 
tion as the medullary rays — 
medullaries radii. 

A medullary pyramid is com- 
posed, then, of straight urin- 

iferous tubes, straight blood-vessels, nerves, a few lymphatics, 

and the apices of the cortical pyramids. 



FIG. 102. Veitcal section through the 
medullary pyramids of the pig's kidney (semi- 
diagramatic). a, trunk of a uriniferous canal, 
opening at the apex of the pyramid, b and c, 
its system of branches. d, loop-shaped urin- 
iferous canals. e, vascular loop, and f, ramifi- 
cation of the vasa recta. (Frey.) 



THE STUDENTS MANUAL OF HISTOLOGY. 



!55 



In the centre of each cortical pyramid is a branch of the 
renal artery from which arise many branches; these soon 
break up into a system of capillaries, — which do not anas- 
tomose, — to make the Malpighian bodies or glomeruli. 

Surrounding this sys- 
tem of capillaries is a 
thin capsule, composed 
of two layers of cells. 
The cells of the inner 
layer are large and flat, 
while those of the outer 
layer are smaller and not 
so flat. This capsule of 
the glomerulus, Bow- 
man's capsule, is the 
dilated commencement 
of one of the uriniferous 
canals. It becomes con- 
stricted at a point 
opposite the entrance of 
the arterial branch, to 
make the neck of the 
capsule. It then dilates 
into a broader tube, be- 
coming convoluted for a 
short distance when it is 
arranged in a more or less 
spiral course ; its direc- 

FIG, 104. Capsule of the glomerulus, rabbit's kidney, tion is then towards the 

Silver treated and tinged with carmine, a, endothelial ... 

cells, d, nucleated, b, vas afferens. vas efferens. medulla, When it ShOltlV 
(after Ludwig.) 

assumes a straight direc- 
tion to the apex of the cortical pyramid, forming the de- 
scending side of the loop of Henle. It now turns sharply 
on itself — the loop of Henle — and pursues a straight direct 




i56 



THE STUDENTS MANUAL OF HISTOLOGY. 




FIG. 105. Diagrammatic view of the Malpighian 
bodies and tubes of the kidney. (Sappey.) 

i, i, 2, st'aight tube of Bellini. 3, 3, 3, other straight 
tubes opening into the tube I, I. 4,4,4,4,4, Mal- 
pighian bodies. 5, 5, 5, 5, 5, convoluted tubes. 6, 6, 
6, 6, 6, descending portions of the looped tubes of 
Henle. 7, 7, 7, 7, 7, ascending, larger portions of the 
tubes of Henle. 8, 8, 8, 8, 8, 8, communicating 
tubas. 9, 9, dotted line showing the limits of the cor- 
tical and of the pyramidal substance. 



course toward the exter- 
nal cortical layer, forming 
the ascending side of the 
loop of Henle. It is 
then again arranged in 
a more or less spiral 
course, becoming later 
very irregular and poss- 
essed of a small lumen. 
It now pursues a con- 
voluted course and be- 
comes united with a 
medullary ray by an in- 
termediate portion — the 
connecting canal — the in- 
tercalary portion. The 
medullary ray soon be- 
comes a straight urin- 
iferous tube, and opens 
on the free surface of a 
papilla; the union of 
these two makes one 
collecting tube. 

From the dilated com- 
mencement of the /urin- 
iferous tube at the Mal- 
pighian bodies to their 
termination in the medul- 
lary rays, they change 
their diameter no less 
than seven times, ist, at 
the constricted portion, 
the neck. 2nd, enlarged, 
in the convoluted por- 



THE STUDENTS MANUAL OF HISTOLOGY. 157 

tion. 3rd, constricted in the descending side of the loop. 
4th, enlarged in the ascending side of the loop. 5th, con- 
stricted at the commencement of the convoluted portion. 6th r 
enlarged during that portion. 7th, constricted at the ter- 
mination in the medullary rays. 

The epithelial cells lining the tubes vary in different 
parts. With the exceptions of the descending side of the 
loop of Henle, the loop itself, and the collecting tube, all 
parts of the uriniferous tubules are lined with epithelial cells, 
composed of a substance which exhibits "rods or fibrils ar- 
ranged vertically to the long axis of the tube." (Heidenhain.) 

In the convoluted portions the cells are nucleated, 
polyhedral, of unequal size and vertically striated. The 
spiral portions are lined with irregular, striated cells; some 
are thin columnar cells, some having concave and others 
convex sides. These constitute the "fungoid cells" of 
Schachowa. 

The descending side of the loop of Henle, and the loop 
itself are lined with flat, thin, nucleated cells, and Klein com- 
pares this structure to that of the capillary blood-vessels, 
only slight differences existing. 

Klein notices a deposit of brownish pigment granules in 
the epithelial cells of the spiral portion of the ascending side 
of the loop of Henle. 

The epithelial cells lining the collecting tubes are nucleat- 
ed, polyhedral, spindle-shaped, flat or angular. 

With the exceptions of the descending side of the loop of 
Henle, 'and the loop itself, there is a membrane covering the 
inner surface of the epithelial cells of all the urinary tubules. 
This membrane is next to the lumen of the tube awd is called 
the " centra-tubular " membrane. (Klein and Smith). 

A study of the physiology of this organ teaches that the 
water of the urine is taken from the blood at the glomeruli, 
that it passes from the capillary system into the dilated com- 



158 



THE STUDENTS MANUAL OF HISTOLOGY. 



mencement of the urinifereous canal, and at last reaches the 
free opening on the surface of the papillae. Klein has dis- 
proved the ideas of Heidenhain concerning the excretion of 

pigment, and has 
demonstrated that 
carmine in ammonia 
injected into the 
circulating blood of 
the cat, will be de- 
posited between, 
and not in, the epi- 
thelial or endothelial 
cells themselves. 

The solid consti- 
tuents of the urine, 
then are excreted 
along the course of 
the uriniferous 
tubes. 

A scanty frame- 
work of connective 
tissue in which are 
seen few cells, per- 
meates the cortical 
substance, being 
more extensive in 
the medullary por- 
tions. 

The arterial sys- 
tem is easily studied 
in well injected specimens. The renal artery enters at the 
hilus and usually divides into four branches, which soon give 
rise to other branches. These pursue a straight course 
through the medullary substance, and having reached the 




. FIG. 106. Thin section of injected kidney of the pig 
■artery, b, afferent and c, efferent vesjels. d, glomeru . 
capillaries, x 20. 



THE STUDENTS' MANUAL OF HISTOLOGY 



159 



boundary lines between the two substances, they bend over in 
such a way that the convexity of the arch looks towards the 
external cortical layer, while the concavity is toward the hilus. 
From the concave side, vessels are given off which are soon 
reduced to the size of capillaries, and which take a direction 
toward the papillae. These are the arterioles, rectce. 

From the convex surface a large 
number of branches arise nearly 
at right angles with the original 
branch. These branches pass 
straight through the centre of the 
cortical pyramid, as far as possible 
removed from the medullary rays. 
They are g'v'ng o r f branches con- 
tinually on either side, the vas 
afferens glomeruli which soon 
break up into capillaries without 
anastomoses. The venous 

system is more complicated. 
While, as a rule, there is but one 
efferent vessel to each Malpighian 
body, yet not unfrequently two, 
three, and rarely four are seen 
emerging from the capsule at a point corresponding to the 
entrance of the artery. These vessels form long, narrow 
meshes around the medullary rays, and narrow circular ones 
around the convoluted tubes. The majority of these capillaries 
are collected into venous branches which usually accompany the 
coil bearing artery. A system of capillaries seen in the medul- 
lary portion arises mainly from the dividing of efferent vessels, 
coming from Malpighian bodies lying deep in the kidney. 
They permeate the whole of the medullary substance and form 
a net-work around the openings of the collecting tubes on the 
papillce. 




FIG. 107. From the kidney of the pig 
(semi-diagramatic). a, arterial branch, b, 
afferent vessels of the glomerulus, c. d, 
vas efferens. e, breaking up cf the same 
into the straight capillary plexus of the 
medullary ray. f, rounded plexus of the 
convoluted canals, i, g, commencement 
of the venous branch. (Frey). 



i6o 



THE STUDENTS MANUAL OF HISTOLOGY. 



Nerves and lymphatics are not wanting. 

METHODS OF EXAMINING. 

Sections of the fresh kidney may 
be made with a Valentin's knife, or a 
freezing microtome. The most in- 
structive views are obtained only 
from hardened injected specimens. 
The kidney of the rabbit or pig may 
be injected with little trouble from 
the renal artery. Prussian blue or 
carmine will give good results if only 
the injection be continued for some 
time in order that all the capillaries 
of the glomeruli may be completely 
filled. The vein may be injected at 
the same time. After the injection 
the organ should be cut into eight or 
ten pieces, placed in Miiller's fluid, 
and in two or three weeks transferred 
to alcohol, to complete the hardening. 
The sections should be cleared in 
oil of cloves, and mounted in 
dammar. If desired, they can be 
slightly stained in hematoxylin be- 
fore clearing. 

It is quite difficult to inject the 
kidney from the ureter, and if the 
injection be a success, the specimen 
will not show to any great advantage; 

FIG. 108. The vascular arrangement of the kidney in 
vertical section, a, arterial branch at the margin between 
the cortex and medulla, b, coil-bearing artery, c, vasa 
afferentia of the glomeruli, d, capillary reticulum of the 
external cortical layer, e, vein of this part, f, elongated 
capillary net-work of the medullary rays, g, rounded net- 
work around the convoluted unniferous canals of the cor- 
tical pyramids, h, venous branch of the cortex, i, efferent 
vessels of the deepest glomeruli, k, their capillary net- 
work. I, venous tubes of the medulla, m, capillary net- 
work of the papilla. (Ludwig.) 




THE STUDENTS' MANUAL OF HISTOLOGY. l6l 

for owing to the convoluted course of the canals and their 
dense arrangement, it is quite impossible to trace the course 
of one tube for any considerable extent. The tubes may be 
separated by teasing, if the interstitial connective tissue be 
previously destroyed. 

This may be accomplished in a measure by boiling in 
acids, or by macerating the section for 12 or 14 hours in muri- 
atic acid, to which has been added water till the acid has ceased 
to smoke. It is then washed and placed in distilled water for a 
day, when the tubes may be isolated by careful teasing. For 
isolating the tubes the following method of Henle's is quite 
successful : Sections of fresh kidney are placed in a flask 
partly filled with a mixture of eight parts of common alcohol 
and two parts hydrochloric acid. The cork of the flask is 
pierced with a long glass tube. The specimen is boiled in 
this mixture for several hours, when the fluid is poured off 
and distilled water added. After seven or ten days, 
the pieces can be carefully teased with needles. 

The epithelium of the tubes is best studied in the kidney 
of the mature foetus. Small pieces are placed in a one per 
cent, solution of potassic bichromate for two weeks. Thin 
sections are washed in water, and slowly stained with carmine. 



CHAPTER XIV. 



The Lymphatics. 

THE lymphatic vessels are quite peculiar in this respect^ 
that while they indirectly withdraw the fluid which they 
contain from the blood-vessels, they eventually return it to 
them by their terminal vessels. The lymphatic vessels in form 
and structure ordinarily agree with the blood-vessels, their walls 
being, perhaps, a trifle thinner and more transparent. Valves 
are met with similar to those of the veins. The vety smallest 
lymphatics consist of a single layer of nucleated cell-plates 
like those of the capillary blood-vessels, and are brought to 
view by the staining action of a nitrate of silver solution. 
When it is considered how very delicate the walls of these cap- 
illaries are and how colorless their contents, it is understood 
why they are dissected with such great difficulty. For their 
examination artificial injections are requisite. Hyrtl came to 
our relief in offering the very effective method known as his 
" puncturing method." If a tissue is thought to contain lym- 
phatics, the fine point of the syringe or injecting apparatus is 
carefully forced into the tissue and the mixture allowed to 
pass into it carefully and slowly in the hope that a wounded 
lymphatic may be injected. Several trials may be necessary 
but finally the object is accomplished. By staining the central 
tendon of the diaphragm with the silver nitrate solution open- 
ings of not inconsiderable size are seen between the epithelial 
cells. These openings — stomata — never exceed the size of an 

162 



THE STUDENTS MANUAL OF HISTOLOGY. 



163 



epithelial cell and are always as large as a red blood-cor- 
puscle. 

This rich plexus of openings is doubtless subservient to 
the absorption of the fluids of the peritoneal cavity. 

a 




FIG. 109. Central tendon of the diaphragm of the rabbit, 
capillaries, b, serous canals, x 250. 



a, lymphatic 



Recklinghausen demonstrates these openings in the fol- 
lowing manner : Milk is injected into the peritoneal cavity of 
a mammal (rabbit.) A cork ring is pressed against the central 
tendon from the thoracic side and needles are passed through 
the tissue into the cork ; in this way the surface of the tendon 
is procured in an absolutely uninjured state, and it can now In- 
excised without difficulty or harm and transferred to the stage 



164 



THE STUDENTS' MANUAL OF HISTOLOGY. 



of the microscope. If a drop of milk be placed on the sur- 
face, the globules may be seen to enter the lymphatic vessels. 
The openings are so small that only two, or at most three glo- 
bules can enter abreast. They are quite round and usually 
lead perpendicularly into the lymphatic vessels. Thus the 
great serous cavities of the body may be regarded as giving 
origin in some regions to the lymphatic vessels. 

THE LYMPHATIC GLANDS. 

The lymphatic glands appear oval or circular, or as is 
quite generally the case, bean- 
shaped. Each gland is surround- 
ed by a sheath, which is composed 
of two strata of connective tissue. 
Direct prolongations of the inner 
stratum penetrate into the gland 
as membranous septa, radiating 
toward the point where the lym- 
phatics emerge. These septa 
communicate freely with one 
another laterally, and having en- 
tered the gland for a certain 
distance they break up into trabec- 
ule which anastomose with one 
another to form small meshes. 
The part of the gland containing 
the septa is called the cortex, the part containing the trabec- 
ule, the medulla. 

The gland tissue, or the adenoid tissue of His, fills the 
meshes in the cortex and the medulla. In the cortex these 
meshes are oval and the enclosed gland tissue is called a fol- 
licle, and in the medulla, medullary cylinder. The follicles 
and medullary cylinders are never in close contact with the 
sheath and septa ; a space is always left, the lymph sinus of 




FIG. 1 10. Lymphatic canal. a, cell 
plates. b, spaces between the same. 
Silver staining, x 400. 



THE STUDENTS' MANUAL OF HISTOLOGY. 



I6 5 




His. These sinuses, both in the medullary and cortical por- 
tions intercommunicate. The adenoid tissue has a like 
structure wherever it is found. There is a matrix of dense, 

reticulated net-work 
ot fine fibrils, called 
the adenoid reticu- 
lum. The endo- 
thelial cells demon- 
strated on this retic- 
ulum are quite 
readily removed by 
pencilling. 

The meshes of the 
adenoid reticulum 
contain one or more 
lymph corpuscles, 
which appear iden- 
tical with the white 
blood-corp u scles 
with this difference : 
their nuclei are much larger. But believing the nucleus to 
represent the living part of the cell, this is what we would ex- 
pect to find. When the corpuscle is young (lymph corpuscle) 
it has a large nucleus, when it is older the nucleus is smaller 
(white blood-corpuscle), and when quite old, the nucleus is 
very small or has disappeared altogether (red blood-corpuscle). 
The blood-vessels of the tissue enter the hilus and reach 
the interior of the organ to terminate in a rounded capillary 
net-work. 

Upon entering a gland the lymph takes the following 
course : From the afferent vessel it passes into the capsular 
net-work, from here into the cortical and then into the medul- 
lary sinuses, from these into the net-work of the lymphatics at 
the hilus and finally into the efferent trunk. Besides these 



FIG. 111. Section -through one of the smaller lymphatic 
glands, with the current of the lymph— half diagrammaticfigure. 
a, the capsule, b, septa between the follicles of the cortex (d) 
c, system of septa of the medullary substance as far as the hilus 
of the organ, e, lymph tubes of the medulla, f, lymphatic 
passages, which surround the follicles and flow through the 
spaces of the medulla, g, union of the Utter into an afferent 
vessel (h) at the hilus. (From Gray.) 



i66 



THE STUDENTS MANUAL OF HISTOLOGY. 



there are various lymphoid organs in the body, either single x>r 
grouped, which are nearly identical with a lymphatic follicle. 
The following are among the number : the glands and fol- 
licles of the mu- 
cous membrane 
of the stomach 
and large and 
small intestines, 
the tonsils, the 
follicles of the 
conjunctiva. 
Peyer's glands, 
thymus gland, 
and also the 
spleen. 

The tonsils are 
covered with 
pavement epithe- 
lium, beneath 
which is connec- 
tive tissue con- 
taining oval or 
spherical lymph 
follicles. The 
thymus gland 
consists of masses of adenoid tissue anastomosing into a net- 
work. 

Peyer's glands consist of a number of aggregated lym- 
phoid follicles. In a single Peyer's patch may be fifteen or 
twenty of these follicles. They are often seen projecting into 
the lumen of the tube as convex bodies between adjacent villi 
or perhaps a few villi are scattered over them. The follicles 
are extraordinarily supplied with capillary blood-vessels which 
permeate them in a radial direction. 




FIG. i 12. Follcle from a lymphatic gland of the dog, in ver- 
tical section, a, reticular framework of the more external, b, of the 
internal portion, c, fine reticulum of the surface of the follicle. 
d, origin of a larger, and e, of a finer lymph tube, f, capsule, 
g, septa, k, division of the one. i, investment space and its 
tenter-fbies. h, vas afferens. I, attacnment of the lymph tubes 
to the septa. (From Gray,) 



THE STUDENTS' MANUAL OF HISTOLOGY. 



167 



The vermiform process must be regarded as an enor- 
mously developed Peyer's plate (Frey.) 



THE SPLEEN. 



The spleen is surrounded by two membranous coats, a 
serous one derived from the peritoneum, and a stronger, 
highly elastic fibrous one. This fibrous membrane sends septa 
into the interior of the organ after the manner of the other 




FIG. 113. Vertical section through a human Peyer's patch; a, intestinal villi, b, Lieber- 
kilhnian glands, c, muscular layer of the mucous membrane, d, apex of the follicle, f, basis 
portion, g, lymph-passages around the follicle, i, at the base of tne same, k, lymphatics of the 
sub-mucous tissue. I, lymphoid tissue of the latter. (After Frey.) x 32. 

lymphatics. In the soft spleen substance are seen cylindrical 
masses of adenoid tissue, averaging about the -fe of an inch 
in diameter, and surrounding the arterial branches. These 
are the malpighian corpuscles or the lymphatic follicles of the 
spleen. 

In some cases these follicles are situated on the side of 
the arterial wall, or the vessel may pass directly through their 
centre, or what is most generally the case, the blood-vessels 
are situated excentrically, surrounded by a greater amount of 



i68 



THE STUDENTS MANUAL OF HISTOLOGY- 



adenoid tissue on one side than on the other. Branches ex- 
tend into the corpuscle from the blood-vessel. Now the ex- 
ternal connective-tissue coat of the small arteries becomes 
transformed into lymphoid tissue, so that these Malpighian 
corpuscles represent localized expansions of this external coat. 
The meshes are filled with lymphoid cells, and capillaries are 
freely supplied. 




FIG. I 14. Small artery, to which IVLlpgniun corpuscles are attached, x iO. 

(Kolliker.) 

In the spleen pulp are a number of nucleated, branched 
connective-tissue cells, often containing pigment granules in 
their interior. These cells have no regular size or form, but 
serve as a support to the soft pulp tissue. Besides these there 
are red and white blood-corpuscles and also larger colorless 
corpuscles in the interior of which are the remains of from one" 
to many red corpuscles (see figure 19.) 



THE STUDENTS MANUAL OF HISTOLOGY. 



169 



The small arteries terminate in capillaries, which, after a 
time, loose their cell walls, for, gradually, processes are seen 
extending from them to unite with the processes of the con- 
nective-tissue cells mentioned above. Here, then, is first a 
blood-vessel with loose branched cells for a wall, and finally 
this even disappears and we have but a channel for the blood 
in the soft pulp with no walls to confine it. The veins 
commence in the same way that the capillaries end. Thus 
in passing through the spleen the blood must come in im- 
mediate contact with the pulp tissue. (See origin and death 
of the red blood-corpuscle.) 




FIG. 115. Thin section of spleen pulp, showing the mode of origin of a small vein. 
Chromic acid preparation, a, the vein tilled with blood-corpuscles, b, blood-corpuscles filling 
the interstices and in continuity with a. c, branched cells. The shaded bodies in the vein are 
the white corpuscles. (Quain.) 

LYMPH CAPILLARIES. 

The lymph capillaries are related to the tissue in which 
they originate as follows : They commence in a system of 
lacunae which are united with each other by larger or smaller 
canals. This is the lymph-canalicular system of von Reckling- 
hausen. The spaces are filled with a soft, semi-fluid substance 
in which are found the migratory connective-ssitue cells ; the 
stable cells, uniting with their processes to form the walls Of 



170 



THE STUDENTS MANUAL OF HISTOLOGY. 



these spaces ; they are continuous with the endothelial wall of 
the lymph-capillaries. This lymph-canalicular system is very 
generally distributed in the different organs of the body, dif- 
fering but slightly wherever found, owing to the arrangement 
of the matrix of the part. In the lungs, bone, cornea, serous 
and synovial membranes, the system consists of lacunae, lined 
with cells as described above. In tendon, fascia, muscle and 
nerve, it consists of long straight channels between the con- 
nective-tissue bundles and fibres. In the skin and mucous 
membranes it consists of inter-fascicular spaces, irregular in 




FIG. 116. From the spleen of the hedgehog; a, P'-lp, with the intermediate currents. 
b. follicle, c, boundary layer of the same, g, its capillaries, e, transition of The same into the inter- 
mediate pu p-current. f. transverse section of an arterial branch, at the border of the Malpighian 
corpuscles. (Frey.) 

shape and situated between bundles of fibres as they cross and 
recross each other. It will be remembered that the walls of 
the blood-capillaries permit particles to pass through their 
stomata into the surrounding connective-tissue. Such par- 
ticles pass at once into the lacunae, lined by the loose, 
branched connective-tissue cells ; from this lymph-canaficular 
system they pass very readily into the lymph capillaries. 

The reasons why a current should be directed from the 
blood-vessels to the lymphatics are these : first, the pressure 
in the blood-vessels is considerable while in the lymphatics it 
is nothing ■ and second, the blood-vessels are in the centre of 



THE STUDENTS MANUAL OF HISTOLOGY. 171 

an area while the lymphatics are at the periphery, hence the 
tendency of the lymph to travel the intervening systems (von 
Recklinghausen.) 

In inflammation it is well illustrated how formed matter 
passes from the blood-vessels into the lymph-canalicular 
system and from here to the lymphatics (Cohnheim and 
others.) Arnold introduced Berlin blue into the blood-vessels 
of living rabbits and frogs, and afterwards traced the pigments 
through the lymph-canalicular system directly into the lym- 
phatics. 

METHODS OF EXAMINING. 

For the injection of the lymph sinuses the puncturing 
method of Ludwig should be followed. This consists in 
thrusting a fine needle point of the syringe into the tissue 
anywhere and in forcing the injecting fluid into it, letting it 
go wherever it will. To be successful this method requires a 
large experience and the student must expect a good propor- 
tion of failures at the start. After injection the tissue is 
hardened in alcohol. Nitrate of silver used as an injection or 
external application demonstrates the cellular structure of the 
lymphatic canals. This method is easily carried out by using 
the mesentery of some small animal, as the cat or rabbit ; a 
piece of the mesentery is stretched on cork, the endothelial 
cells removed by pencilling, the silver solution applied, and 
the specimen treated as recommended for all silver staining. 

The glands of some of the lower animals, dog, cat, are 
hardened in alcohol, and the thin sections slightly stained. 
Glands placed first in M tiller's fluid and subsequently in alco- 
hol harden well and are very suitable for section-making. To 
examine the framework the sections should be very thin and 
thoroughly pencilled. 



172 THE STUDENTS' MANUAL OF HISTOLOGY. 

A natural injection of the lacteals is easily procured by- 
killing an animal, as a cat, about four or five hours after a 
hearty meal of milk. The entire lacteal system will be found 
fully distended with the digested fat. 

Sections of Peyer's patches, with injected blood-vessels 
are readily made after alcohol hardening. 

The lymph passages of the mesenteric glands of the ox 
can be beautifully injected by the puncturing method. 



CHAPTER XV. 



Nerve Fibres and their Modes of Termina- 
tion. 

A SIMPLE classification of nerve fibres can be made by- 
dividing them into two general classes. First, those 
having the axis cylinder surrounded by a medullary sub- 
stance, and second, those consisting of the axis and sheath 
alone. 

MEDULLATED FIBRES. 

These are by far the most generally distributed. They 
present the greatest variation in size ; some are as large as 
the l2 1 00 of an inch, while others are not half the size, and if 
examined near their origin or termination they may be no 
larger than the i4 ^ of an inch. Every medullated nerve 
fibre is now known to consist of three parts; i, the sheath; 2, 
the medullary substance; 3, the nerve axis. The investing 
membrane consists of a fine, transparent, homogeneous, con- 
nective-tissue, known as " the sheath of Schwann," " limiting 
membrane of Valentin," "primitive sheath," "neurilemma." 
It corresponds to the sarcolemma of muscle. It covers the 
medullary substance wherever it exists and forms a protecting 
envelope to the delicate nerve axis throughout its whole 
length, save at its very origin and termination. It is not seen 
without the use of reagents. Here and there at quite regular 
intervals is a nucleus. 

173 



174 



THE STUDENTS MANUAL OF HISTOLOGY. 



The medullary substance completely surrounds the nerve 
axis and occupies all the space between it and the neurilemma. 
It is known as "the white substance of Schwann," "the mye- 
line," "nerve medulla," etc. It is composed of a peculiar com- 
bination of albuminoid bodies, is 
homogeneous and transparent 
when fresh, and is capable of 
greatly refracting the light. If 
the nerve be allowed to dry, or if 
one of many reagents be allowed 
to come in contact with it, the 
medullary substance coagulates 
and becomes very opaque, com- 
pletely hiding the axis from view. 
This gives a very peculiar and 
characteristic appearance, and the 
fibre is said to become "varicose." 
The axis cylinder is seen in a 
transverse section of a bundle of 
nerves as a small cylindrical body 
occupying from one-fifth to one- 
fourth the diameter of the entire 
fibre. It is the sole essential con- 
stituent of the nerve. It exists 
alone at the very commencement 
and termination of all nerve 
fibres. It is not readily seen in 
the fresh nerve without reagents, 




Medullated nerve fibres. 
A, from frog, fresh specimen, a. nodes 
of Ranvier. b. nucleus. B, node of 
Ranvier, osmic acid preparation. a, 
sheath of Schwann. b, medullary sub- 
stance, c, axis cylinder. C, nerve fibre 



treated with alcohol, the axis cylinder is u uf :„ VPr v pacilir Hicr^rn^H in 
protruding from the sheath. A and C DUL 1S VerV eaS11V OlSCemea in 

x 4 oo. b X750. stained transverse sections of the 

spinal chord. Besides pale granules in the axis, certain re- 
agents bring out well-marked longitudinal striae. They are 
compared to the longitudinal striae of muscle, dividing the 
nerve, as the muscle, into the " primitive fibrillae " of Schultz, 



THE STUDENTS' MANUAL OF HISTOLOGY. 



175 



h. 



J 51 



or into the " axis fibrillae " of Waldeyer. After the study of 
the modes of termination of these fibres, additional proof will 
be seen that each nerve axis is a bundle of most delicate 
fibrils. 

Situated at quite regular intervals on these fibres are 
constrictions, which, for a long time, were supposed to be due 
to the methods of manipulation. Ranvier has shown these 
" constriction rings " to exist in many different animals, and 
that about midway between two of these 
constrictions is a nucleated nerve cor- 
puscle. Thus it is in mammals, birds 
and amphibia, while in fishes the number 
of nuclei is greater. This makes a nerve 
fibre composed of a number of long 
narrow cells placed end to end, each cell 
possessed with one nucleus, or in the 
fishes with many nuclei. Here, then, at 
each constriction ring, nutrient matter 
may find a place to enter the highly en- 
dowed axis, and the results of decompo- 
sition find an exit. The nerves of the 
body consist of a greater or less number 
of nerve fibres united together by a connective tissue, called 
the perineurium, which corresponds to the perimyseum of 
muscle. 



> : tt 

i LJ 

FiG. 118. 
nerve fibres. 1 
brain, x 400. 



Varicose 
from the 



METHODS OF EXAMINING. 

Cut out a small piece from the sciatic of the frog and 
place on the glass slide, add a drop of chloroform and tease 
carefully. Then add more chloroform and cover with thin 
glass. If the chloroform evaporates add more. This reagent 
dissolves the oily medullary substance and brings the axis 
cylinder into view. 

Prepare another specimen and add strong acetic acid. 



176 THE STUDENTS' MANUAL OF HISTOLOGY. 



The substance of the fibres will retract except the axis, which 
will protrude from the end sufficiently to be studied. 

A piece of a small nerve is carefully cut out and placed 
in a 1 per cent, solution of osmic acid. Care should be taken 
not to injure the nerve in any way. Let it remain in this reagent 
about four hours, or until it is stained black. Then wash 
thoroughly in water and tease in dilute glycerine. Add 
haematoxylin and let it remain on the specimen until it is col- 
ored well. Wash in dilute acetic acid and examine in glycer- 
ine. Unless stained too deeply, all parts of the fibre can be 
made out. The medullary sheath will appear black from the 
osmic acid staining, and the constriction rings will look like 
breaks in the deep coloring. At intervals the axis cylinder 
will be seen stained with the haematoxylin, as will also the 
nuclei of the neurilemma. 

Take a small piece of nerve and add caustic potash or 
soda. This will render more fluid the nerve- 
medulla, and if pressure be applied to the cover- 
glass, it may be forced out of the tubes in large 
fat-like drops. Then the primitive sheath may 
be seen. By teasing a nerve-trunk, many times 
the needles will cause a displacement of the con- 
tents of the sheath, so that the latter is brought 
to view for a short distance, much as the sarco- 
lemma is seen under like circumstances. Silver 
staining will demonstrate the nuclei of the sheath 
to good advantage. A 5 p. c. solution should 
be used and the fibres allowed to remain in it 
only two or three minutes when they are treated 
cyiir l l der," 9 ni^ie a ^ ter tne usual fashion for silver staining. 

of silver prepara- 

gSnar'^stna-" NON-MEDULLATED FIBRES. 

tion. x 1000. 

Early in the history of the foetus the nerve fibres of the en- 



THE STUDENTS MANUAL OF HISTOLOGY. 



177 



tire system are of this class. The olfactory nerve of man and 
of all vertebrates is composed exclusively of these fibres. 
They also form a large part of the sym- 
pathetic system. These fibres consist of 
an axis cylinder closely surrounded by a 
nucleated sheath. Remak discovered 
them first as composing entirely the thick 
splenic nerves of ruminants. For this 
reason, these fibres are often called 
" Remak's fibres." Remak has named 
them "ganglionic fibres." They are 
most generally found in the invertebrata. 
Under the microscope they are not so 
FIG ' 2a , Non-mediiiiared bright as the other class, but look gray 

nerve fibres from sympathetic. 

moo- and gelatinous. The neurilemma is very 

firmly united to the axis, and is of firm consistence itself. 
For a bundle of these fibres can be teased apart without harm. 





FIG. 121. Ganglia cells, a, apolar. b, unipolar, c, bipolar, d, unipolar cell, with 
nucleated cell capsule which is continued over cell process as the sheath of Schwann. 
x 250. 



THE STUDENTS MANUAL OF HISTOLOGY 



These are procured for study from the cervical sympathetic 
of an animal, or from the sympathetic nerves of the frog, 
which lie along the vertebral column in close connection 
with the aorta. They are treated as described for medullated 
fibres, although simple hematoxylin staining answers well, 
staining the nuclei in a beautiful manner. 

CEREBROSPINAL GANGLIA. 

The frame-work of these ganglia is of connective-tissue, 
supplied by the dura-mater and arachnoid, and is supplied 
freelv with blood-vessels. The cells are spherical or irregular- 
ly oval, and are of all sizes. Each cell is provided with a 
nucleus, and many times a nucleolus. The majority erf 
writers give to these cells but one process. As this process is 
directly connected with a nerve axis, it is called the axis cylin- 
der process. The substance of the cell being composed of 
minute fibres, intra-cellular fibrils, this process must be con- 
sidered as a prolongation of these. Some cells do not have 
even one process; they are apolar. Each ganglion cell is sur- 
rounded closely by a membrane lined with nucleated cells ; 
these are continued along the axis cylinder process to make 
the nerve corpuscles beneath the neurilemma. The mem- 
brane itself extends over the axis cylinder as the sheath of 
Schwann. A medullar} 7 substance may or may not be sup- 
plied. 

SYMPATHETIC GANGLIA. 

These are very like those of the cerebro-spinal system 
with this distinction. Cells are present here from the apolar 
to the multipolar. No matter how many processes may be 
given off, each one is a continuation of the cell substance, and 
receives a prolongation from its capsule with its lining cells.. 



THE STUDENTS MANUAL OF HISTOLOGY. 



179 



MODES OF TERMINATION. 

An interesting question arises concerning the modes of 

termination of the nerve 
fibres in the different tissues 
of the body. First of all 
must be considered how the 
nerves divide on their way 
to the periphery. When 
near its peripheric extremity 
the fibre divides usually into 
two branches, each of which 
may divide again and again, 
until from ten to thirty or 
more branches arise from 
the one, or one fibre may 
suddenly break up into a 
number of branches at once. 
Briicke and Miiller were the 
first to observe these modes 
of division. Belharz has 
told us that in the electric 
eel a single medullated fibre 
extends from the medulla 

FIG. ,„. Ganglion cell from the sympathetic of oblongata tO each of the 
thehyla or green-tree frog a, cell body, bj sheath. t e l ectr i c organs, and 111 

c, straight nerve fibre. d, spiral fibre, contmua- » ' 

tion of the forme., e ; and of the latter, f, order fa^ eaQ ^ electric plate 

may have a terminal fibre, it must divide millions of times. 

As ,a result of each of the divisions, the axis cylinder 
becomes proportionately smaller, so that the sum of all the 
nerve axes of the terminal branches of any given fibre will ex- 
actly equal the original axis. This is not true of either the 
medullary substance or sheath of Schwann ; these increase 
soon after division, until each of the branches is nearly as 




i So 



THE STUDENTS MANUAL OF HISTOLOGY. 



well supplied with them as was the original fibre. Both the 
neurilemma and medullary substance disappear sooner or 

later, and are absent 
in the ultimate fibrils. 

TERMINATION IN 
STRIPED MUSCLE. 

When one of these 
nerve branches 
reaches a muscle fibre 
the following changes 
occur: The neuril- 
emma of the nerve 
becomes continuous 
with the sarcolemma 
of the muscle, and 
the medullary sub- 

FIG. 123. Muscular nerves of the frog, showing division of stance Ceases, while 
•the fibres, a, into two, b, into three branches. X350. (After f\iQ axis aDDearS tO 
Koliiker. rr 

rest on a peculiar, nucleated, rounded plate. This plate is 
concave within and convex without to conform with the muscle 
fibre. On it are from four to twenty nuclei. This is the ter- 
minal plate of Krause, or the nerve end-plate of Kuehne. 
Viewed in profile this end-plate presents a regular convex 
elevation — " Doyere's mount." As soon as the axis reaches 
this end-plate, it breaks up into a number of antler-like 
branches, or into several minute fibres, which form a net- 
work with one another. Into some of these end-plates two 
nerve fibres enter. They differ in size, and many muscle 
fibres have more than one of them. 

IN UNSTRIPED MUSCLE. 

When a nerve fibre reaches the unstriated muscle in which 
it is to terminate, it divides into a number of non-medullated 




THE STUDENTS MANUAL OF HISTOLOGY. 



181 



branches. The axis cylinders of these branches now divide 
and collect in small groups, and by a re-arrangement of their 
fibrils form a plexus — "the ground plexus of Arnold." 

Branches of this plexus divide into still smaller branches 
to form "the intermediary plexus of Arnold." These branches 

are distributed to the 




separate bundles of 
unstriped fibres. Al- 
though these branches 
are so very small, yet 
they are composed of 
a number of primitive 
fibrils. They now 
break up into the 
smallest branches 
which penetrate the 
substance that lies be- 
tween the individual 
cells. A net-work is 
formed here by anas- 
tomosing branches. 
These are the "mus- 
cular fibrils of Kebs." 
Farther than this, it is 
difficult to trace these 
We have nev- 
able to 



see 



FIG. 124. Two muscular filaments from the psoas of the _, .. 
Guinea-pig, with the nerve terminations; a, b. the prim- Fibrils, 
itive fibres and their continuation into the two terminal plates , 

e, f c, neurilemma with nuclei, d. d, and passing over into the er been 
sarcolemma. g, g. h, muscular nuclei. (Frey.) ,, . ... , 

anything like the ter- 
minations to be described. 

Frankenhausen describes still finer branchlets given off 
from this net-work, which terminate in the nucleolus of each 
cell. 

Elischer says they terminate in a blunt, enlarged point on 
the surface of the nucleus. Klein thinks their termination in 
the nucleus not improbable. 



182 



THE STUDENTS MANUAL OF HISTOLOGY. 



IN TENDONS. 

Here the nerve axis divides into fine branches, which 
again divide into the most minute elementary fibrils, to form 
a close net-work. The terminal end is embedded sometimes 
in a nucleated substance something like the end-plate in mus- 
cle. (Rollett.) 

Bulbs are seen in some tendons like those found in the 

conjunctiva. (Golgi). In 
the sheath of tendon one 
observer has described 
bulbs having the appear- 
ance of small Pacinian 
corpuscles. 

In the conjunctiva are 
the terminal bulbs of 
Krause. These are ellip- 
tical-shaped bodies with 
a nucleated envelope, en- 
closing a hyaline sub- 
stance, in which are a 
few nuclei, although no 
cells can be perceived. 
Upon entering this bulb 
the nerve fibre loses its 
medullary substance, and 
the axis passes through 
the substance to the op- 
posite pole and termin- 
ates in a slight enlarge- 

FIG. 125. Two muscle fibres from hyo-glossus of frog. ^1 

a, nerve end-plates, b, nerve fibres leaving the end-plate, ment. I ney are llOt eaS- 
c, nerve fibres terminating after dividing into several ■■, , 1 . • 

branches, d, a nucleus in which two nerve fibres anas- UV Seen, anQ tneir eXlSt- 
tomose. x 600 (Klein and Smith. • ■ ' , • , , 

ence in man is denied by 




some investigators. Nothing can be said concerning them 
from personal observation. 



THE STUDENTS MANUAL OF HISTOLOGY. 



1 3 3 



The Pacinian bodies were described as long ago as 1741, 
but were soon forgotten to be rediscovered in 1830 by Pacini. 
These are elliptical bodies averaging ^ of an inch, and pre- 
sent to the touch a firm, tense structure. In man they are 
found in the palm of the hand and in the sole of the feet. 
The mesentery of the cat is an admirable place to procure 
them, many times in great quantities. The capsule is marked 
by concentric striations, which in turn denote their connec- 
tive-tissue membranes. On the inner surface of this capsule 

K 




FIG. 126. End bulb of the conjunctiva of man. a, node of Ranvier, b, nerve 
nucleus, c, sheath of Schwann, d, sheath of Henle. e, branches of the axis cylinder, 
h, granular substance witn nuclei, x 700 (Key and Retzius.) 

there is a single layer of flat cells. When the nerve fibre en- 
ters this body it loses its medullary substance, the neurilemma 
becomes continuous with the capsule, and the axis cylinder 
enters alone, terminating in a divided extremity, or undivided 
in a pear-shaped swelling. 

The axis cylinder is striated most beautifully in a longi- 
tudinal manner, showing it to consist of primitive fibrillar. 
Around this terminal fibre is a transparent, striated, semi-fluid 
central matrix. Between the layers of the capsule are capil- 



1 84 



THE STUDENTS MANUAL OF HISTOLOGY. 




FIG. 127. Pacinian corpuscle from long 
mesentery of the cat. x 35. 



lary blood-vessels. Specimens are 
very frequently obtained showing a 
capillary entering the corpuscle with 
the nerve. 

In the skin there are the tactile 
corpuscles of Meissner and terminal 
nerve fibres. The tactile corpuscles 
are most numerous on the palmar 
surfaces of the hands and fingers, 
and plantar surfaces of the feet and 
toes. On the third phalanx of the 
index finger Meissner counted one 
hundred and eight in a space ^ of 
an inch square. They are oval- 
shaped bodies about -3-J-g of an inch 
In the capsule are longitudi- 
nally and transversely arranged nu- 



clei. The nerve axis alone 
enters this body and ter- 
minates in curved or 
looped windings. It is 
difficult to decide pre- 
cisely how these fibres 
end, whether in a 
branched extremity or in 
a bulbous enlargement. 
Many times several fibres 
or pale axes are seen 
pursuing an oblique or 
longitudinal direction in 




FIG. 128. T/vo human nervous papillae from the skir 



the Central nart- nf fV,^ of the volar surface of the index finger. In the interior of 

ccnudi pan 01 me the papi||ae is the tacti|e body) jnto the tjssues of whjch 

COrpUSCle. the nerve fibres enter. (After Kolliker.) 

Other nerve fibres, after forming a plexus just beneath 



THE STUDENTS' MANUAL OF HISTOLOGY. 185 

the rete-mucosum, give off branches which form a minute 
fibrillar net-work just beneath the epithelial layer. 

In mucous membranes this fibrillar net-work probably 
exists. In the cornea are two systems. The deep system ter- 
minates in the true corneal tissue as a net-work, while from this 
a superficial net-work arises, which penetrates the covering of 
epithelial cells, and terminates just beneath the superficial 
layer of flattened cells either as a fine net-werk or in blunt 
ends. The terminal fibres do not enter into any relation 
with the cells themselves (Klein). For the termination of 
dental nerves see chapter on teeth. For the terminations 
of nerve fibres of the various organs of the body, consult 
the articles on those subjects. 



CHAPTER XVI. 



T 



Spinal Cord. 
HE spinal cord is surrounded by the dura mater, arach- 
noidea, and pia mater. Between the last two is a 

spongy tissue, consisting of 
smaller and larger tra- 
beculae of connective-tissue. 
This is the subarachnoidean 
tissue. 

The ligamentum denticu- 
latum extends between these 
two membranes the whole 
length of the cord. It is situ- 
ated midway between the 
anterior (ventral) and poste- 
rior (dorsal) nerve roots di- 
viding the subarachnoidean 
space into anterior and pos- 
terior spaces. 

The spinal cord is the 
cylindrical elongated cord 
contained in the spinal canal. 
In length it is from sixteen 
to eighteen inches, and de- 
void of its membranes its 
weight is about an ounce 
and a half. It is .a column 
of nervous tissue commenc- 
ing above at the foramen 
magnum and terminat- 
ing below on a level with the first lumbar vertebra in 
a conical filament of gray matter termed the filum termi- 

186 




FIG. 129. Transverse sect'onsot the spinal cord 
Df 1, the horse. 2, the ox. 3, man. 4, the dog. 5, 
frie frog. All x 2. 



THE STUDENTS MANUAL OF HISTOLOGY. 



I8 7 



nale. It is marked by two enlargements, the one com- 
mencing at the third cervical and extending to the first 
dorsal, called the cervical enlargement, and corresponding 
to the. origin of the nerves that supply the upper extremities. 
The other is opposite the last dorsal vertebra and corresponds 
to the origin of the nerves supplying the lower extremities, 
known as the lumbar enlargement. 

A longitudinal fissure extends along the whole length of the 
cord in the anterior median line — the anterior median fissure. 
A like fissure extends along the posterior median line — the pos- 
terior median fissure. This divides the cord into two equal parts, 
which are united in the centre by a transverse band of nervous 
tissue. The anterior median fissure is shallower and wider than 
the posterior, and does not extend to the centre of the cord. 
It reaches to about one-third the thickness of the cord and 
is lined completely by a reflection of the pia mater. 

a 




FIG. 130. Diagram of transverse section of the spinal cord, a, anterior, b, posterior median 
fissure, c, anterior, d, posterior cornua, e, central canal, t, anterior, g, middle, h, posterior col- 
umns-; k, anterior, I, posterior, nerve-roots. 



THE STUDENTS MANUAL OF HISTOLOGY. 



The posterior fissure is not so distinct as the anterior, 
but extends nearly to the centre, this also receives a fold 
of the pia mater. The two surfaces of this reflected fold 
often become united so that the fissure is obliterated. 

FRAME-WORK OF THE CORD. 

Prolongations of the pia mater not only enter the fissures 
but also minute septa between sec- 
tions of the white substance. They 
carry blood-vessels with them. A 
semifluid, homogeneous substance fills 
all the interstices between the nerve 
substance proper of the cord. This 
is the neuroglia matrix of Klein. 
There are also minute fibrils, forming 
g a net- work, quite similar to elastic tis- 
sue, neuroglia fibrils. These fibrils 
pursue a longitudinal direction in the 
white substance, but every direction 
in the gray. There are present also 
branched, nucleated, connective-tissue 
cells. The "neuroglia" of the cord 
is composed of all three, matrix, fib- 
rils, and cells. The greater the one 
of these parts, so much the greater 
the others. The amount of neuroglia 
varies in the different parts of the 
cord. 

WHITE SUBSTANCE. 

A thin transverse section of the cord 
reveals two substances, a central or 
gray substance, resembling in shape a 
fig. i 3 i. Transverse section of capital H, and a peripheral or white 

human spinal cord at different ■, rrn i •. i_ . 

heights, a, upper cervical, b, substance. The white substance 

cervical en'argement. C, dorsal. r . ■> <<■ * .* j < ^ 

D lumbar enlargement E, sacral Of each half Of the COrd may be 
^coccygeal, (partly from Quain). divided intQ three co l umns . T he ante- 




THE STUDENTS MANUAL OF HISTOLOGY. 



189 



rior (ventral) column includes all that part of the cord which 
is bounded internally by the anterior median fissure, exter- 
nally by the anterior cornu and the nerves emerging from 
it to give rise to the anterior spinal nerves, and posteriorly 
by the gray substance. It is continuous with the anterior 
pyramids of the medulla. The lateral column is bounded 







7\y 





W 



FIG. 132. Transverse section of one-half of the spinal cord of a dog. x 15. 



internally by the gray matter, and anteriorly and posteriorly 
by the anterior and posterior cornua. It is continuous with 
the lateral column of the medulla, and is much the largest 
of the three columns. 



190 THE STUDENTS MANUAL OF HISTOLOGY. 

The posterior (dorsal) column is bounded internally by the 
posterior median fissure and externally by the posterior 
cornu. This is directly continuous with the restiform body 
of the medulla. 

Besides the neuroglia and its nutritive system of vessels, 
nerve fibres are seen running mostly in a longitudinal direc- 
tion. In a transverse section of the cord the white sub- 
stance appears composed entirely of these minute cylinders 
cut across. The axes of these fibres take the staining 
readily, and each one is seen surrounded by a transparent 
zone which represents the myeline. Just external to this is 
the frame-work of the cord, for there is no positive evidence 
of a sheath of Schwann. Not all of these fibres, how- 
ever, pursue^ a horizontal direction, for in a transverse 
section, just at the base of the anterior median fissure, a 
band of nerve fibres is seen passing horizontally from the 
gray matter of one side to the white of the other ; this is 
the anterior white commissure. 

This commissure makes a direct connection between the 
white matter of one side and the gray matter of the oppo- 
site side. Still other fibres are seen passing from the gray 
matter of the anterior cornua into the white matter of the later- 
al tracts, also similar fibres from the posterior cornua pursuing 
the same oblique direction. Horizontal fibres pass from 
the posterior nerve roots into the gray matter of the poste- 
rior cornua, and some of their fibres having their origin 
in the anterior cornua pass obliquely through the white sub- 
stance to form the anterior nerve roots. 

THE GRAY SUBSTANCE 

is represented by the Latin capital H, and presents two 
anterior and two posterior cornua. The anterior cornua 
are thicker, blunter, with a serrated appearance at the mar- 



THE STUDENTS MANUAL OF HISTOLOGY. 



191 



gin, and they do not extend to the surface of the cord. 
Here are found the largest nerve cells in the body. In a 
well stained specimen of the spinal cord of the dog in the 
author's possession these large cells are visible to the 
naked eye. They are arranged in three groups, inner, 
anterior, and lateral, named in the order of the size of 
their cells. The cells are large, with branched and 




FIG. I33. Nerve cells from anterior horn of the spinal cord of the ox. Obtained from fresh 
specimen by staining with haematoxyhn. x 150. 



unbranched procesess, having a nucleus and nucleolus sur- 
rounded by a membrane with an intranuclear net-work (Klein). 
The unbranched processes are known as "axis-cylinder" pro- 
longations. While there is usually one, there may be two of 
these in one cell They ultimately receive a medullary 
substance and sheath to form a nerve fibre. Cells are 
known as apolar, unipolar, bipolar and multipolar, accord- 
ing to the number of processes or poles proceeding from 



192 THE STUDENTS' MANUAL OF HISTOLOGY. 

them. Small nerve cells are found here which exist in 
greater numbers in the posterior cornua. 




FIG. 134. Nerve cell from anterior horn of the human cord, a, axis cylinder process. 
(Gerlach). x 150. 



The posterior cornua are narrower and longer, extend- 
ing nearer to the surface than the anterior. Near their 
termination is an enlargement, named from its appearance, 
substantia gelatinosa. At the base of the posterior cornua, 
internally, a little back of the central canal is a mass 
of cells, restricted nearly to the dorsal region, known as 
Clarke's column. 

A little anterior to the middle of the commissure 
that connects the two parts of the cord is seen the 
central canal which varies in diameter throughout the whole 
length of the cord. In carefully prepared specimens 



THE STUDENTS MANUAL OF HISTOLOGY. 



193 




it is visible to the naked eye. It is in 
communication above with the fourth 
ventricle and extends below to the ter. 
mination of the cord. It is lined with cili- 
ated, columnar, epithelial cells which have 
a long, slender filament extending into 
the connective-tissue, which surrounds 
the canal just outside the cells. The 
space between the filaments of these cells 
and the connective-tissue is filled with a 
fine granular substance, which Gerlach 
fig. 135. Waii of the believes to be "connective-tissue, devoid 

central canal of the spinal 

cord, a, connective tissue, of elastic fibre net-work." A few nuclei 

b, fine granular substance. 

c, ciliated ceii in way of devei- are seen here, from which probably will 

opment. d, ciliated epithe- . •* 

Hum. (Geriach.) be develope 1 new epithelial cells. In early 

life this canal is filled with a fluid, — the cerebro-spinal 
fluid — but in the adult the canal is more or less com- 
pressed by the proliferation of the cells, and not capable 
of holding so much fluid. Anterior to the central canal, 
between it and the anterior white commissure, is a band of 
gray matter, the anterior gray commissure. Posterior to 
the central canal, between it and the base of the posterior 
median fissure is a similar band of gray matter, the poste- 
rior gray commissure. 

Beside the cells in the gray matter, there is a minute 
net-work of fibrils known as " Gerlach's nerve net- work." 
This net-work is composed of minute primitive nerve fibrils, 
some of which have been seen to anastomose with the ulti- 
mate branches or divisions of nerve fibres from the poste- 
rior nerve root. All the branched processes of the nerve 
cells anastomose with Gerlach's nerve net-work. Nerve cells 
in the anterior cornua are attached to this net-work, while 
at the same time they are attached, through their axis- 
cylinder prolongations to medullated nerve fibres. Although 



194 TH E STUDENTS* MANUAL OF HISTOLOGY. 



the nerve cells in the posterior cornua anastomose with 
Gerlach's net-work, there is no direct union with nerve fibres. 

Some of the nerve fibres originating in the anterior 
cornua pass to the lateral tracts and proceed direct to the 
brain as longitudinal fibres, not attached to any ganglion 
cells. (Klein). 

Numerous fibres pass horizontally through the anterior 
portion of the posterior horns. (Gerlach. Brauch). 

Bundles of fibres run longitudinally through about the 
middle of the posterior horns (Smith). 

In the dorsal region are bundles of fine fibres from 
Clarke's columns of ganglion cells running in three direc- 
tions, i, backward, 2, crossing each other, and 3, passing 
in an outward direction (Gerlach). 

The spinal cord is well supplied with blood-vessels. 

METHODS OF EXAMINING. 

Many methods are given for preparing the cord for study. 
The following method is in constant use at this laboratory : 
The cord is removed carefully from its bed and cut at 
once, with a razor wet with alcohol, into pieces about 
% of an inch in length. These are immediately placed 
in a large amount of Miiller's fluid. In a few days they 
are taken out and stripped of their membranes. This 
is not done at first from fear of injuring the soft tissue. 
They are replaced in the fluid where they can remain for 
an indefinite length of time without injury, or in a few 
days more may be placed in alcohol where they remain 
for three or four days, when they are transferred to abso- 
lute alcohol ( until the requisite hardness is obtained. This 
is discovered by repeated trials although it will not vary far 
from twenty-four to thirty-six hours. If over-hardened 
the sections crumble ; if not hardened sufficiently the 
tissue springs, and only thick sections can be obtained. 
The piece is usually embedded, and then either held in the 



THE STUDENTS MANUAL OF HISTOLOGY. 



95 



hand or placed in the microtome, the tissue and razor 
being flooded with alcohol. The thin section is now slightly 
washed by allowing a few drops of water to flow over it. 
Hematoxylin, carmine and aniline blue are valuable color- 
ing agents. When carmine is used, it is better to dilute 
Beal's carmine one-half with water and to allow the sec- 
tions to remain in it from two to twelve hours. For class 
work, it is used full strength, and the specimens remain in 
it from fifteen to thirty minutes. Distilled water is now 
flowed over the section until the excess of carmine is 
removed, when a few drops of a one per cent, solution of 
acetic acid are added. This is removed and alcohol sub- 
stituted, which is replaced by absolute alcohol in about 
fifteen minutes. In about five minutes this is removed 
and the oil of cloves added. In a short time the speci- 
mens have cleared, when they are preserved in dammar. 
This gives great contrast between the two substances of 
the cord, stains the cells, their nucl i and nucleoli and 
the axis-cylinders in a most beautiful manner. Fresh speci- 
mens may be placed in the freezing microtome, the sections 
stained, and satisfactorily examined immediately. There 
are many valuable methods of treating the cord for exami- 
nation; these are given in full in our works on microscopic- 
al technology. 



CHAPTER XVII. 



The Brain. 

THE neuroglia of the brain is quite similar to that of the 
spinal cord. There are a few differences, e. g. in the 
white matter are seen small round cells between bundles of 
fibres, which are collected in masses in certain parts of 
the brain, as in the olfactory lobes. Boll describes connec- 
tive-tissue cells in the gray matter surrounding the blood- 
vessels. Duke Charles, of Bavaria, says that there are color- 
less blood-corpuscles around these vessels both in disease 
and in health. The membrane lining the ventricles of 
the brain is a continuation of that lining the central canal 
of the spinal cord and is covered with a similar layer of 
ciliated cells. It is an accumulation of neuroglia, and is 
known as the ependyma. 

WHITE MATTER. 

In the white substance of the brain the nerve fibres are 
medullated as in the spinal cord, but are without any 
sheath of Schwann. Some of these fibres are extremely 
minute, while others are of medium size. These fibres con- 
nect the different parts of the brain substance as follows : 

i. Those uniting the gray matter of the hemispheres 
with the large cerebral ganglia. 

2. Those uniting identical parts of the two hemispheres 

e. g. corpus callosum. 

196 



THE STUDENTS MANUAL OF HISTOLOGY. 



197 







3. Those joining dif- 
ferent parts of the 
same hemsiphere. 

4. Bundles of fibres 
connecting the hemis- 
pheres with the cere- 
bellum. 

We owe our present 
knowledge largely to 
Meynert, the highest 
authoritiy on these 
subjects. He regards 
those fibres that unite 
the gray matter of the 
cerebrum with the 
large cerebral ganglia 
as the projection sys- 
tem of the first order. 

Those fibres which 
pass between the cere- 
bral ganglia and the 
gray matter around 
the ventricles, he 
considers the pro- 
jection system ' of 
the second order. 
These are motor fibres 
passing through the 
crus cerebri and the 
pons into the white 
substance of the cord. 
The nerve fibres com- 
posing the roots of the 

FIG. 136. Transverse section 
from a sulcus of the 3d frontal 
convolution of man. x 100. 
(Charged from Meynert). Th« 
medullary substance is not given in 
the drawing. 



I98 THE STUDENTS' MANUAL OF HISTOLOGY. 

cerebral nerves he regards as the projection system of the 
third order. 

GRAY MATTER. 

Meynert classifies the gray matter under the following 
four divisions : 

1. The cortex of the cerebral hemispheres. 

C Corpora striata. 

, Tne.argecerebra. ganglia %g$jg£*« 

[ Corpora quadrigemina. 
( Rhomboidai fossa. 
3. The gray substance of thel Aqueductus sylvii. 
medulla I Tuber cmereum. 

Gray matter lining ventricles. 
t Infundibula. 
4. The cortex and central gray matter of the cerebellum. 
Here in the gray matter is a fibrillar net-work correspond- 
ing to Gerlach's nerve net-work in the spinal cord. Multi- 
polar ganglion cells are met with everywhere, varying in 
size and generally possessed of one unbranched process, the 
axis cylinder, which becomes a medullated nerve fibre. 
In the cortex of the cerebral hemispheres are the follow- 
ing five layers of Meynert : 

1. Neuroglia and nerve net-work with small multipolar 
ganglion cells. 

2. Small, pyramidal, closely crowded ganglion cells. 

3. Numerous large ganglion cells, not crowded. These 
cells have (a), a branched process directed towards the 
surface, (b) branched lateral processes, (c) an axis-cylinder 
process in the centre of the basis processes. 

4. Small irregular ganglion cells with few branched pro- 
cesses. He regards the first three layers as containing the 
motor cells and the last layer as connected with sensory 
nerves. 

5. Branched, spindle-shaped ganglion cells parallel to 



THE STUDENTS MANUAL OF HISTOLOGY. 



99 



the surface. All of these cells have a nucleus and gener- 
ally a nucleolus. 

Meynert gives the following deviations from this rule : 

i. In the gray matter of the posterior portion of the 

occipital lobe about the sulci hippocampi there are eight 

layers. The prominent feature here is small multipolar cells 

"the granular formation of Meynert." 

2. In the cortex of the hippocampus major the small 
cells of the fourth layer are wanting. The second and 
third layers are the chief elements. 




FiG. 137. Ganglia cells from cerebral convolutions, x 400. 

3. In the walls of the fossa sylvii the fifth layer is most 
prominent. 

4. In the bulbus olfactorius there is a central cavity 
lined with ciliated cells. The upper part is composed of 
white matter, the lower of gray matter. This gray matter 
consists of the following four layers from below upwards. A. 



THE STUDENT S MANUAL OF HISTOLOGY. 



non-medullated nerve fibres which pass into the olfactory nerve. 
B, a layer of glomeruli; each glomerulus consisting of a convolu- 
tion of an olfactory nerve fibre with many nucleated Deiter's 
cells. C, multipolar ganglion cells, spindle or pyramidal shaped. 
D, a net-work of fibrils with groups of nuclei. 

In all these ganglia the cells are multipolar; spindle- 
shaped in the optic thalami and containing pigment in the 
corpora striata. 

CELLS OF THE GRAY MATTER. 

The ganglion cells of the gray matter are multipolar, and by 
their axis-cylinder processes give origin to the cerebral nerves. 
They are collected together in groups, each group giving origin 
to some particular nerve. The group of cells or " nucleus " of 
the optic nerve is a collection of multipolar cells of many sizes. 
The "nucleus" of the motory root of the fifth is situated in the 
anterior portion of the fossa rhomboidalis. They are large 
multipolar cells containing pigment. The cells are smaller in 
the sensory nucleus. In the " nucleus " of the facial, in the 
outer part of the superficial olivary body and on the floor of 
fourth ventricle, are very large multipolar cells. The "nucleus" 
of the acoustic nerve is in the fossa rhomboidalis near the sur- 
face. In the lateral anterior part of this fossa is the "nucleus" 
of the abduceus. Situated in this fossa also are the " nuclei " 
of the glosso-pharyngeal and vagus. The cells are spindle- 
shaped. The cortex of the cerebellum shows five layers. 

i. A matrix of fibrillar nerve net-work and fine branced 
processes passing to the surface from the deeper layer of cells 

2. Large, spindle-shaped ganglion cells, Purkinje's cells. 
These cells have two processes. A branched process 
extending into the above layer and an unbranched or axis- 
cylinder process passing deeper. 

3. A nuclear layer. This is between the second layer and 
the white substance. It is composed of minute fibrils with 
a great number of spherical nuclei. The corpora dentati 



THE STUDENTS MANUAL OF HISTOLOGY. 



and olivary bodies are composed of a fine nerve net-work and 
slender multipolar ganglion cells. The brain is rich in blood- 
vessels. 

METHODS OF EXAMINING. 

Two methods are quite useful for examining fresh brain. 
Each of these methods has iis advantages. 

The first method will be found in full in the September 
number of the Monthly Microscopical Journal, vol. XVI, page 
105, by Bevan Lewis. His method is briefly this : There are 
three stages of the process. 

1. The preparatory stage, which consists in making 
as thin vertical sections as possible of the gray mat- 
ter. The specimen is held in one hand between the 
thumb and fingers and with a sharp razor in the other, by a 
sweeping cut tolerably thin sections can be obtained. The 
upper surface of the knife should be deeply concave and kept 
flooded with alcohol. These sections are floated on a slide 
and a few drops of Muller's fluid placed over them. This is 
allowed to cover them completely and to make a pool around 
them for some seconds. The cover glass is then applied and 
by aid of a pencil or strongly mounted needle, steady gentle 
pressure is made on the centre of the cover until the nervous 
matter becomes a thin transparent film. The superfluous fluid 
is removed by rinsing in water and the slide is then transferred 
to alcohol. In about thirty or forty seconds the slide is re- 
moved from the dish of alcohol and while one edge of the 
cover-glass is steadied by the fingers, the blade of a penknife 
is gradually inserted beneath the opposite edge. The thin 
film will be left floating on the glass-slide or adhering to the 
cover-glass. The specimen is washed to free it from spirit by 
inclining the slide and allowing drops of water from a large 
camel's hair brush to flow over it. 

2. The staining stage. A drop of a 1 per cent, solution 
of aniline black is placed on the film and as soon as the re- 



202 THE STUDENTS' MANUAL OF HISTOLOGY. 

quisite color has been acquired, the slide is transferred to a 
vessel containing water and gently lowered in it. By gently 
moving the water above it with a brush the superfluous dye 
floats away. Other staining agents, notably carmine, may be 
used. 

3. The mounting stage. All fluid is drained off the 
specimen and it is placed under a bell jar with sulphuric acid. 
When perfectly dry add oil of cloves. This is removed when 
it has rendered the film transparent and dammar added and 
then the cover glass. 

The Sankey method. Another excellent method was de- 
scribed in the April number of the Quarterly Microscopical 
Journal of 1876. Sections are cut as by the above method, 
only they may be as thick as the one-tenth of an inch. They 
are stained in a 7 p. c. solution of aniline blue-black. In three 
hours the staining is removed and water added until it washes 
away the excess of the staining. The specimens are floated 
on a clean slide, allowed to drain, and then exposed to the air 
in a dry place for twenty-four or forty-eight hours. At the 
end of this time the section will be firmly dried to the glass. 
It is now in a condition to have its upper surface planed off 
with a razor or other suitable instrument, taking care not to 
scrape the specimen away at any place. Dammar is added 
(oil of cloves not necessary) and the cover-glass applied per- 
manently if an examination of the specimen is satisfactory. 
The nerve-cells usually show to good advantage by this 
method. 

The brain may be hardened by processes recommended 
for the spinal cord. A 2 or 3 p. c. solution of bichromate of 
ammonia is a useful hardening agent. Small portions placed 
in Mailer's fluid and then in alcohol are suitable for study. 



CHAPTER XVIII. 



Testicle and Ovary. 

THE TESTICLE. 

THE testes are small glandular bodies from one and one- 
half to two inches in length, one inch in breadth and one 
and one-fourth inches in their antero-posterior diameter. 

The testes appear very early in fcetal life as two ovoid 
bodies situated at the inner borders of the Wolffian bodies. 
Two ducts are seen at their outer borders ; the inner one, the 
duct of the Wolffian body, becomes the vas deferens of the 
male and disappears in the female ; the outer one, the duct of 
Mtiller, becomes the fallopian tube in the female and disap- 
pears in the male. 

The coverings of the testicle are described fully in the 
general works on anatomy. The minute structure of the 
gland substance only will occupy our attention. 

When viewed with the naked eye the substance is of a 
reddish-yellow color, and is divided into a number of pyram- 
idal lobes, the bases of which are directed toward the sur- 
face of the organ. Their number has been variously estimated 
at from 250 to 400. They vary in size according to the num- 
ber of convoluted tubes they contain, for each lobe has from 
one to five or even more tubes — tubuli seminiferi — thrown into 
coils which are loosely held together, so that by careful dis- 

203 



204 



THE STUDENTS MANUAL OF HISTOLOGY. 



&*wiJS/&*$ 



section under water they can be disentangled to a considerable 
extent. It is estimated that 840 of these tubes are in each 
testicle and that each tube is on an average 30 inches in 
length and from ¥ J- ¥ to y^- of an inch in diameter. 

Each tube commences by several blind extremities or by 
anastomosing loops. Their walls consist of several layers of 

epithelial cells. The tubes 
from the different lobes 
sometimes anastomose with 
each other. Sometimes the 
several tubes of each lobe, 
together with tubes from the 
adjoining lobes unite to- 
gether to form one canal. 
In this way about twenty 
canals are formed in each 
organ. At first these canals 
are quite tortuous but as 
they pass toward the poster- 
ior surface of the testes they 
become nearly straight — 
vasa recta- — when they pass 
through the mediastinum 
forming a close net-work of 
tubes — the rete testis. 

The mediastinum is 
formed by a prolongation of 
the fibrous covering of the 
testis {tunica albuginea) into the posterior border of the gland 
and from this septum proceed the septa of fibrous tissue that 
divide the gland into its numerous lobes. Having traversed 
the substance of this fibrous septum the tubes leave the organ 
by from 12 to 20 canals known as the vasa efferentia. These 
tubes are about the -^ of an inch in diameter and have walls 




FIG. 138. Vertical section of the testicle to show 
the arrangements of the ducts. (Gray.) 



THE STUDENTS MANUAL OF HISTOLOGY. 205 

of fibrous tissue and muscle cells. At first these vessels are 
quite straight but as soon as they increase in size they become 
exceedingly convoluted. 

The epididymis is the long narrow body lying along the 
outer edge of the posterior border of the testis. It consists of 
an upper, enlarged extremity, the globus major, which is 
united to the testis by the vasa efferentia ; also a lower ex- 
tremity, the tail or globus minor, and also a central portion or 
body. After leaving the testicle the vasa efferentia form small 
cone-shaped masses — coni vasculosi— which together consti- 
tute the globus major of the epididymis. These soon unite in 
one convoluted tube to form the body and globus minor of 
the epididymis. When this tube is unravelled it measures not 
far from twenty feet in length ; at its commencement it is 
about -fo of an inch in diameter ; it is reduced to -^ of an inch 
before reaching the globus minor, however it soon increases in 
size again. It is lined with ciliated columnar cells and its 
walls, thin at first, are thick and well provided with muscle 
cells toward its lower end. The motion of the cilia is in an 
outward direction (Becker.) 

After leaving the globus minor the duct turns upon itself 
to form the vas deferens. This tube is about two feet in 
length and on an average -J- of an inch in diameter. It is very 
hard and cordy to the feel and it extends from the globus 
minor along the inner surface of the epididymis, behind 
the spermatic cord to the internal abdominal ring. From here 
it passes into the pelvis, down the side to the base of the blad- 
der, where it unites with the duct of the seminal vesicle of the 
corresponding side to form one of the ejaculatory ducts. The 
vas deferens is lined with columnar epithelial cells, without 
cilia. 

The seminal-vesicles — vesicuhe seminales — are composed 
of convoluted tubes, which, when unravelled, are three or four 
feet in length, and lined with short prismatic epithelial cells. 



206 



THE STUDENTS MANUAL OF HISTOLOGY. 



The vas aberrans of Haller is a small elongated mass, 
composed of a single convoluted tube, which is given off from 
the lower part of the epididymis as a diverticulum of the canal 
forming that body. When unravelled the tube varies from 
two to fourteen inches in length. It represents the remains 
of one of the tubes of one of the Wolffian bodies which still 
remains attached to the excretory duct. In the commencing 
portion of the vas deferens is the organ of Girardes. It is 
known also by the name of parepididymis ; it is made up en- 
tirely of canals. 

The seminal tubes in the adult testis are lined with several 
layers of epithelial cells, called the seminal cells. 

Those cells situated next to the walls of the tube are 
known as the outer cells and those situated near the lumen 
are the inner seminal cells. 




FIG. 139. A portion of the wall of a seminal tubule of the testicle of the dog. 
a, seminal cells, b, spermatoblasts, c, earliest stage in the format'on of the spermato- 
zoa, d, spermatozoa more fully developed. (Klein and Smith.) x 450. 



Klein notices two kinds of cells in the outer layer : i, 
those having an oval transparent nucleus limited by a mem- 
brane and provided with one, two or three nucleoli ; 2, those 



THE STUDENTS MANUAL OF HISTOLOGY. 



207 



with a spherical nucleus, the cells smaller than the former, and 
the nucleus not limited by a membrane. 

The inner seminal cells contain in their matrix a convo- 
lution of rods, twisted in various directions and anastomosing 
with one another. The nuclei of the cells nearest the lumen 
of the tube very frequently undergo division, the cells them- 
selves dividing afterwards. Not unfrequently multinuclear 
cells are seen with from six to ten nuclei. Each nucleus is 
spherical in shape and is not limited by a membrane. 




FIG. 140. Spermatozoa, a, of the blaps mortisago. b, of the house-mouse, c, of 
the bat. d, of the sheep, e, of the Raja batis. f, of man. 

As these cells become developed into the spermatozoa, 
they have been named by Sertoli, the spermatoblasts. Study- 
ing one of these cells with a spherical nucleus, it is noticed, 
first, that the nucleus becomes limited by a membrane and is 
placed near the edge of the cell. The nucleus looses its retic- 
ulated appearance and its substance becomes collected in 
one part so that a clear space, a clear tube, is left. The nu- 
cleus becomes gradually more disc-shaped, and the cell sub- 
stance is drawn out into a club-shaped granular body which is 



208 THE STUDENTS' MANUAL OF HISTOLOGY. 

separated from the nucleus by the clear space mentioned 
above (Klein.) By other gradual changes the epithelial cell 
finally becomes a fully developed spermatozoon, which has a 
well defined oval head, behind which is the middle-piece of 
Schweigger-Seidel, attached to which is the tail ending in a 
very fine pointed extremity. 

The nucleus of the inner epithelial cell has become the 
head of the spermatozoon, the granular body has become the 
tail, and an outgrowth of the nucleus has become the middle- 
piece. From the researches of H. Gibbes, [Quarterly Journal 
of Microscopical Science, Oct., 1879] we learn that each sper- 
matozoon of many of the vertebrates consists of [1] a long, 
pointed head, [2] an elliptical structure joining the head, 
[3] a filiform body, [4] a fine filament much longer than the 
body and connected to it by [5] a homogeneous membrane. 
When living this filament is in constant motion and has a con- 
tinuous waving from side to side. He is " confident that the 
substance of which the head is composed shows a different 
chemical reaction to the rest of the organism." The waving 
filament was seen in the spermatozoa of the following mam- 
mals: The horse, dog, bull, cat, rabbit, guinea-pig, and man. 

He draws the following conclusions : 

1. That the head of the spermatozoon is enclosed in a 
sheath which is a continuation of the membrane which sur- 
rounds the filament and connects it to the body. 

2. That the substance of the head is quite distinct in its 
structure from the other parts and that it is readily acted upon 
by alkalies ; these reagents having no effect on the other parts 
except the membranous sheath. 

3. That the motive power lies in a great measure in the 
filament and the membrane attaching it to the body. 



THE STUDENTS MANUAL OF HISTOLOGY. 



2O9 



THE OVARY. 

The tissues of the hilum consist of connective-tissue, 
blood-vessels, muscle cells, etc. 

Covering the free surface of 
the ovary is a layer of short, 
columnar, nucleated epithelial 
cells, the " germinal layer" of 
Waldeyer. In the cortical por- 
tion of the ovary there is a 
layer of tissue free from ova , 
this has been named by Henle 
the tunica albuginea. Spindle- 
shaped cells are met with as 
well as branched cells. Besides 
these cells there are groups of 
nucleated, polyhedral cells ; 
Balfour regards these cells as 
the remains of the epithelial 
cells of the Wolffian bodies, as 
do also His, Waldeyer and 
others. The Graafian follicles 
are of many sizes and shapes. 
The smaller ones are situated 
near the surface, just beneath 
the albuginea ; while the larger 
ones are in the deep seated 
portions of the organ. The 
small follicles are so closely 
and densely arranged just un- 
der the albuginea that they 
constitute a distinct layer, the 
"cortical layer" of Schronn. 

I. Two fully developed spermatozoa. 

horse, b, of the triton cristatut. ArOUIld tllC larger follicles the 

(H. Gibbes.) 




2IO 



THE STUDENTS MANUAL OF HiSTOLOGV. 



spindle-shaped cells are arranged concentrically, forming 
an investment to the follicle, the " tunica fibrosa" of Henle. 
Each follicle is surrounded by a membrana propria, in which 
are seen a few nuclei. Just beneath this layer is one of 
epithelial cells, the membrana granulosa, and within 
these cells is the ovum. The membrana granulosa varie 
from a single layer of flat cells in the smaller follicles to 
columnar shaped cells of one, two or more layers in the larger 
ones. 



o—i 




FIG. 142. Portion of.a section of a cat's ovary, a, layer of small ovigerms. b, a 
follicle farther advanced. The ovum is covered with the cells of the discus proligerus. 
x 35- 

The ovum of the fully developed follicle lies in a mass of 
cells which project from the membrana granulosa like a 
mound. This projection is called the discus proligerus. In 
the smaller follicles the pvum is surrounded by a mass of cells 
which are everywhere in close contact with the membrana 
propria, but soon a fluid appears between some of the cells, 
causing little cavities which increase in number and size until 
these several inter-cellular cavities become confluent and the 
ovum at last becomes separated from the membrana propria, 
except where it remains connected by the intervening discus 



THE STUDENTS MANUAL OF HISTOLOGY. 



proligerus. This fluid is called the liquor folliculi. In this 
fluid are seen occasionally a few small, more or less vacuolated 
cells. They once belonged to the follicular epithelium, but are 
now undergoing retrogressive changes [Klein] and will soon 
disappear. 



ofololffiT 




FIG. 143. Vertical section through the ovary of a half-grown cat. a, germinal epi- 
thelium of the surface, b, albuginea. c, Graafian follicles, x 350. (Klein & Smith.) 

The ovum is the nucleated cell embedded in the discus 
proligerus. Its nucleus is known as the " germinal vesicle " 
and its nucleolus or nucleoli as the " germinal spot or spots." 

The protoplasm immediately surrounding the nucleus is 
more transparent than that at the periphery of the ovum. 
Surrounding the ovum is a clear, transparent ring, the zona- 
pellucida, which, according to Waldeyer and others, often 
shows in the mature ovum a vertical striation caused by the 
continuation as fine threads of the epithelial cells surrounding 
this zone. 

" Many follicles arrive at the stage of ripeness before 
puberty is reached and are subject to a process of degenera- 



212 



THE STUDENTS MANUAL OF HISTOLOGY 



tion. -But this process involves also follicles of earlier stages 
and even the smallest follicles." [Klein and Smith, Atlas of 
Histology, p. 290, 1880.] 

METHODS OF EXAMINING. 

The testis. The familiar process of hardening in Muller's 
fluid and transferring to alcohol is a very satisfactory one for 

this organ. The tubes can be 
teased apart in these prepara- 
tions to good advantage, al- 
though for this purpose the 
method of Sappey is in some 
respects superior, small por- 
tions of the organs are placed 
for one or two days in a mix- 
ture of hydrochloric acid, one 
part, and water two parts, 

By the aid of a fine syringe 
the organ may be injected at 
several points with a 1 per cent, 
solution of osmic acid. The 
specimen is then placed in al- 
cohol, when after a few days it 
is sufficiently hardened to ad- 
mit of thin sections being made 

FIG. 144. Graafian follicle, a. spindle-cells • ,. m, • 

of stroma, b, membrana propria et granulosa, in VariOUS directions. 1 hlS 

c, zona pellucida. d, ovum with its germinal • 1 • 1 1 1 1 

ves.de and germinal spot, x 350. (Kiem and process is highly recommended 
Smith ° by Mihalkovies. 

The Ovary. Beautiful sections of the ovary of the cat 
are in the author's possession, made from specimens hardened 
in Muller's fluid and alcohol, stained with carmine, cleared in 
oil of cloves and mounted in dammar. 

From the fresh ovary of the dog or rabbit, ova may be 
obtained as follows : While the ovary is held firmly in the 




THE STUDENT S MANUAL OF HISTOLOGY. 213 

hand, the most prominent Graafian follicle is pricked and its 
contents received on a glass slide in a drop of normal fluid. 
If present the ovum is easily recognized when it should be 
examined, uncovered and with a low power. Afterwards a 
higher power may be substituted, covering the specimen, but 
inserting beneath the cover a piece of paper to avoid pressure. 



CHAPTER XIX. 



The Tongue, Skin, Lining of the Nasal 
Cavity and the Ear. 

THE mucous membrane lining the mouth is covered with a 
thick layer of stratified epithelial cells ; and among these 
cells are a few that are connected together by fine fila- 
ments, although they are separated from each other by the or- 
dinary cement-substance. When the parts are inflamed, the 
intercellular substance is increased and the connecting fila- 
ments show to much better advantage. These are the 
" prickle-cells " of M. Schultze. In the mucous membrane 
are numerous large mucous glands. The duct of each gland 
is a single layer of endothelial cells and it is a direct contin- 
uation of the basement membrane, which here, as in other 
parts of the alimentary canal, is between the layer of epithelial 
cells and the mucosa. Lining the duct is a layer of nucleated 
columnar cells. Upon reaching the submucous tissue the duct 
divides into a number of branches. These branches are con- 
voluted, and they have one or more short lateral branches. 
The body of the gland is lined with cells identical with those 
lining the mucous salivary glands. When the gland is inac- 
tive these cells are transparent and are filled with mucigen 
which is changed into mucin during secretion. 

The tongue is essentially a muscular organ, covered with 
mucous membrane. On its dorsal surface are three kinds of 

214 



THE STUDENTS MANUAL OF HISTOLOGY. 



215 



papillae; the circumvallace, fungiform, and filiform. The first 
are seen with the unaided eye at the base of the tongue, ar- 
ranged in the form of a V. The second are distributed over 
the surface of the tongue and are visible also to the unaided 
eye. The third are the most numerous as well as the smallest. 
They are not especially concerned in the sense of taste. In 
the circumvallate and in many of the fungiform papillae there 
are peculiar bud or flask shaped organs — the organs of taste — 
the gustatory buds — the taste buds of Schwalbe. They are 
about yi-Q- of an inch high in man, and they exist in large num- 




FIG. 145. I aste buds, a, epithelial surface. (Klein and Smith) X450. 

bers. They are covered externally with one, usually two or 
more, layers of long, tapering, flat cells, which are in close 
contact with each other. They surround the opening of 
the organ above and " stand like the staves of a 
barrel." These peripheral cells surround the central or taste 
cells. The central cells are slender, nucleated and spindle- 
shaped. The nucleus causes an enlargement of the cell at 
that point. The cells terminate above in a rod shaped ex- 
tremity at the opening of the organ; below they terminate in a 
slender often bifurcated extremity which, it is supposed, passes 
as a nerve axis or axis fibrilla into the gustatory nerve. Fine 
nerve fibrils are certainly connected with these taste cells. 
(Englemann, Homgschmied.) 

Situated near the taste buds are serous glands, embedded 
in the mucous membrane. The bodies of these glands are 



2IO 



THE STUDENTS MANUAL OF HISTOLOGY. 



like the parotid 
found in them. 



in structure. There are no mucous cells 
In all probability they secrete a watery sub- 
stance which is poured 
over the parts containing 
the taste buds and thus 
they assist in the distribu- 
tion of the substance to 
be tasted. 

The nerves of the pa- 
pillae contain end bulbs 
(Krause), and the tactile 
corpuscles of Meissner 
can be demonstrated, 
(Geber). 




FIG. 146. Cells from taste buds, a, cover eels, 
b, cellsfrom central part. 1 , the fine extremity which 
projects at the orifice of the bud 2, the deep ex- 
tremity which becomes cont.nuous with fine nerve 
fibrils. (After Englemann and Klein.) 



MUCOUS MEMBRANE 
THE NOSE. 



OF 



Only a portion of this 
membrane (Schneiderian) is of especial interest in this connec- 
tion. The portion which contains the terminations of the 
olfactory nerve is distributed over the upper portion of the 
septum, and the upper and middle turbinated bones. Non- 
ciliated epithelial cells cover this highly vascular membrane in 
these regions, although the ciliated variety abounds in the 
other parts. Glands are scattered freely through the membrane. 
The yellowish appearance of this membrane is due to the 
presence of yellowish granules in the long columnar cells 
covering its surface. These cells send long processes down- 
wards, which usually give off numerous branches which anas- 
tomose with other branches (Martin) from neighboring cells, 
to make a continuous net-work just beneath this layer. Be- 
tween these cells are nucleated, spindle-shaped ones — the ol- 
factory cells of Schultze. One end of these cells terminates in 
a fine process on a level with the surface of the columnar cells 



THE STUDENTS MANUAL OF HISTOLOGY. 



21'/ 



between which they lie; the other end terminates below in a 

fine filament which may be di- 
y I rectly connected with a fine 

axis fibrilla from one of the 
non-medullated fibres of the 
olfactory nerve. 

THE SKIN. 

The importance of this com- 
plex structure of the body is 
very evident when we consider 
the variety of its functions and 
the extent of its surface. It 
forms a protective covering for 
the body; it is an organ of tac- 
tile sensibility, it preserves the 
external forms of the muscles; 
it is an organ of excretion, and 
it aids in maintaining the nor- 
mal temperature of the body. 

FIG 147. 1, Cells of the regio olfactoria of 
■the frog, a, an epithelial cell, terminating be- 111 the Case OI an average Size 
low in a ramified process. b, ol'actory cells . . 

with the descending filament, d, the peripheral mail ltS SUlTaCe IS equal tO SIX- 
rod, c, and the long vibratile ciliae, e. 2, cells, r j r 

from the same region of man. The references teen Square feet, and OI ail 
the same, ">nly snort projections, e, occur (as • , 

artefacts) on the rods 3, fibres o the olfactory average Size WOmail, twelve 
nerve from the dog. At a, dividing into fibrillae. r . 

<Quain.) square teet. 

The skin may be divided into two principle layers: i, 
the true skin or corium, and 2, the cuticle or epidermis. 

The epidermis is divided into the following four layers: 

1. Rete-Malpighii or rete mucosum. 

2. Granular layer (of Langerhaus.) 

3. Stratum lucid urn (Schron.) 

4. Stratum corneum. 

The deep cells of the first layer are columnal and pro- 
vided with nuclei. The more superficial colls arc polyhedral, 




2l8 



THE STUDENTS MANUAL OF HISTOLOGY. 



also nucleated. The lower surface of this layer is uneven and 
presents papillae and corresponding depressions, which adapt 




FIG. 148. Epidermis a, rete-mucosum. b, granular layer, c, stratum lucidum. 
d, stratum corneum. (Smith and Klein.) x25o. 

themselves to the corresponding uneven surface of the true 
skin. The layer of Langerhaus is composed of granular, 
spindle-shaped cells which take hematoxylin staining to an in- 
tense degree. The third layer is 
a translucent one, occasionally 
showing in it a few closely packed 
cells. 

The fourth layer, the most su- 
perficial, is made up of many 
layers of horny epithelial cells, 
without nuclei, as a rule. 
D , , . „-■ * «. * In colored skins the pigment is 

FIG. 149. Polyhedral cells of the rete- r ° 

Maip.ghii connected with each other by fme deposited around the nuclei of the 

filaments. Prickle cells of Schultze. (alter r 

Kiem and Smith.; X550. deeper cells of the rete-Malpighii. 

(Klein.) In this layer are tound the prickle-cells of Schultze. 
The corium, derma, or cutis vera, is protected above by the 
epidermis and is attached to the parts beneath it by a loose 
areolar tissue. Fibrous tissue forms the bases of the true 
skin. Distributed through it are blood-vessels, nerves, glands, 




THE STUDENTS MANUAL OF HISTOLOGY. 219 

hair bulbs, etc. The upper part of this layer is divided into 
papillae which are received in the depressions between the de- 
scending papillae of the rete-Malpighii. In those parts where 
the sense of touch is most delicate there are found the largest 
number of papillae supplied with terminal nerve fibres. These 
are the tactile corpuscle, (see figure 128), found in great 
abundance in the skin covering the palms and soles of the 
hands and feet; less abundant in the skin of the palmar sur- 
face of the forearm and the nipple. Pacinian bodies are 
found in the subcutaneous tissue and " end bulbs"on the glans 
penis and glans clitoridis, and occasionally on the borders of 
the lips. Aside from these special nerve terminations there is 
a superficial plexus of delicate nerve fibrils just beneath the 
rete-mucosum. Many of the cutaneous nerves are distributed 
to the hair follicles. 

The vascular papillae are supplied with either a single 
branch which terminates in a loop, or with several branches 
which anastomose and then return to the veins. 

The lower part of the corium is com- 
posed largely of white fibrous tissue in 
which are seen a few muscular and 
elastic fibres. The hair sacs have been 
described already, (see hair.) 
Situated as a rule in the subcutaneous 
cellular tissue are the sudoriferous or 
sweat glands. They consist of a fine 
tube coiled up after the manner of our 
figure. The tube is lined throughout 
with epithelial cells. \n the walls of 
the tubes are smooth muscular elements. 

F.G. 150. A human sudorifer- The dllCt IS twisted lipoil itself and 
ous eland. (After Klein.) .1 c ,- . 1 1 • >>i 

v ; opens on the surface oi the skin with a 

funnel shaped dilation. 

The sebaceous glands or submucous follicles are situated 




220 THE STUDENTS MANUAL OF HISTOLOGY. 

in the corium generally near the hairs. The sacs composing 
the gland are lined with epithelial cells as are their ducts. 
They open into the hair follicles discharging a thick fatty sub- 
stance. They frequently become enlarged through a closure 
of their ducts, as seen on the face and alse of the nose. 

THE EAR. 

The minute structure of the ear is so very complicated 
that it would carry us beyond the limits of this work to give 
anything like a full description of its several parts. The fol- 
lowing abridged account will enable the student to partially 
understand the terminations of the auditory nerve. The 
essential part of the ear is situated in the petrous portion of 
the temporal bone, and is known as the internal ear or laby- 
rinth. 

The osseous labyrinth consists of three parts ; the vesti- 
bule, the semi-circular canals, and the cochlea. Within this 
labyrinth, but separated from it by a clear fluid, the perilymph, 
are membranous structures in which are found the terminal 
fibres of the auditory nerve. This membranous labyrinth en- 
closes a fluid called the endolymph. 

The vestibule communicates externally with the tympanic 
cavity, internally with the internal auditory meatus, anteriorly 
with the cochlea, and posteriorly with the semi-circular canals. 
Five openings unite the vestibule with the semi-circular canals. 
While one aperture — apertura scalse vestibuli — unites it with 
the cochlea. 

The semi-circular canals are three in number. They are 
of unequal length and they measure -^ of an inch in diameter. 
At one end of each canal is an enlargement called the ampulla 
which is more than twice as large as the tube. The cochlea is 
about one-fourth of an inch in length, and in breadth toward 
the base it is the same. It bears some resemblance to a com- 
mon snail shell. Its conical-shaped central axis is called the 



THE STUDENTS MANUAL OF HISTOLOGY. 



modiolus, which extends from the base to the apex. Its base 
is perforated with numerous orifices through which pass deli- 




FIG. 



The cochlea laid open. (Enlarged.) (Gray.) 



cate nerve fibrils from branches of the auditory. One of the 
orifices larger than the rest is called the tubulus centralis mo- 
dioli. It extends the whole length of the modiolus and trans- 
mits a nerve and artery. 

Surrounding the modiolus in a spiral manner for two 
turns and a half is the spiral canal — laminis spiralis ossea. It 
is about one and a half inches in length and one-tenth of an 
inch in width at its commencement. 

It gradually diminishes in size on its way to the apex 
where it terminates in a closed extremity to form the apex of 
the cochlea, called the cupola. This canal is partly divided into 
two passages or scalae, by a thin flat osseous, membranous 
plate, which winds around the modiolus and projects into the 
spiral tube. These scalae are known as the scala tympani and 
scala vestibuli. 

Within the osseous labyrinth is the membranous one, 
smaller than the former, and separated from it by the peri- 
lymph. It has a general resemblance in form to the vestibule 
and semi-circular canals. It is loosely united to the lining 



222 



THE STUDENTS MANUAL OF HISTOLOGY. 



membrane of these parts by fibrous bands. The mem- 
branous labyrinth forms a closed sac containing the endo- 
lymph. In the vestibule the membranous labyrinth consists of 
two parts, the utricle and the saccule. Attached to the walls 
of these sacs are crystals of carbonate of lime, otoliths or 
otoconia. 




OtoJithi 
temthrougA the wa 



i&io Cochlea 



FIG. 152. The membranous labyrinth deta;hed. (Enlarged.) (Gray.) 

Projecting into the cavity of each of the ampullae is a 
rounded eminence, caused by a thickening of the tunica pro- 
pria. Over this eminence the epithelial lining of the ampullae 
consists of cells of the columnar shape. Between these cells 



THE STUDENTS MANUAL OF HISTOLOGY. 



223 



are spindle-shaped ones which have 
hair-like processes that project into the 
endolymph. 

Branches of the auditory nerve reach 
the tunica propria of the ampullae, when 
the axis cylinders divide into their primi- 
tive fibrillae. These fibrils form a net- 
work just beneath the attached ends of 
A single nerve axis 




FIG. 153. Otoliths. 



the epithelial cells, 
fibril now passes through the long 
axis of each of the spindle-shaped 
cells and terminates in the free hair- 
like processes (Rudinger). Relzius 
gives a different view of these termi- 
nal fibres. He regards the hair-like 
processes as belonging to the colum- 
nar shaped cells, and that the narrow 
end of each of these cells becomes 
continuous with a nerve fibril. The 
membranous labyrinth of the cochlea 
consists of a tube lined with epitheli- 
al cells and enclosing endolymph. 
This tube is divided into three parts 
by two membranes; one of these 
membranes is formed by the prolon- 
gation of the lamina spiralis to the 
outer wall of the cochlea and is call- 
ed the basilar membrane. Stretch- 
ing from this membrane obliquely 
across to the outer cochlear wall 
is the delicate membrane of 

FIG. 154. Diagram of the auditory epithelium and the 
mode of termination of the nerves of the ampullae, a, 
columnar epithelium, b, spindle-shaped cells each sup- 
porting a hair. c, basal supporting cells, d, two nerve 
fibrils. (Quain after Schultze.) 




224 THE STUDENTS MANUAL OF HISTOLOGY, 

Reissner, by its direction enclosing a triangular space, ductus 
cochlearis. 

The epithelium covering the basilar membrane contains 
the so-called organ of Corti. This forms a conical elevation 
and is hollow in its interior. In the centre of this organ are 
two sets of rod-like bodies, rods of Corti, which are so arrang- 
ed as to enclose a space, filled however with endolymph in the 
natural condition. 

On the inner side of each inner rod is a long cell covered 
at its free border with short hairs. This is the inner hair cell 




FIG. 155. A pair of rods of Corti, side view, from the rabbit. a, basilar membrane. 
b, inner rod. c, outer rod. d, nucleated protoplasmic masses. (Quain.) 

of Deiters. Three or four rows of outer hair cells are ar- 
ranged parallel to the "outer rods. 

The cochlear branches of the auditory nerve pass through 
the basilar membrane and are continued as axis-cylinders. 
Some authors state that a single primitive axial fibril passes 
directly into the inner hair cells. Others describe these fibrils 
as stretching across the canal and terminating in the outer 
hair-cells as seen in, figure 156. 

Others that the termination is not in the hair cells, but in 
the "subjacent irregular protoplasmic cells which both in the 
character of their nucleus and in other particulars are not very 
unlike nerve cells." 

METHODS OF EXAMINING. 

The Tongue, The tongue is best studied in hardened 



THE STUDENTS MANUAL OF HISTOLOGY. 



injected specimens. The tongue of the rabbit can be injected 
through the arteries with Prussian blue, hardened in a two 
per cent, solution of potassic bichromate or in a weak solution 
of osmic acid and the thin sections tinged with hematoxylin. 

The sections should be cut vertically to the mucous mem- 
brane, and mounted in glycerine or dammar. 

The sections show to the best advantage if a double stain- 
ing be practiced. To accomplish this the sections are placed 
first in a saturated solution of picric acid for about twenty 
minutes, then they are placed in the hematoxylin. 

To study the branched muscle fibres small pieces of the 
tongue are boiled in water a short time, when the fibres can be 
teased apart readily. 




FIG. 



156. Organ of Corti, (dog). a, basilar membrane, b, outer hair cells, 
inner hair cells. d, nerve, e, nerve fibril. (After Waldeyer.) 



The taste-buds are studied in specimens that have been 
immersed for several days in a two per cent, solution of 
chromic acid, to which has been added an equal volume of 
glycerine. These preparations are carefully picked under the 
microscope. Specimens that have been in Miiller's fluid for 
15 or 20 days are in good condition to be picked. 

To study the nerve terminations chloride of gold (.5 p. a), 
chromic acid (.02 p. a), and osmic acid (1 p. c.) preparations 
are to be preferred. 



226 THE STUDENTS' MANUAL OF HISTOLOGY. 

The Skin. The skin over the palms of the fingers is in- 
jected from some large vessel in the hand or fore-arm; and 
vertical sections are made either from the fresh specimens with 
the freezing microtome, or, better still, from specimens hard- 
ened in a mixture of chromic acid and alcohol [chromic acid 
Yz per cent, solution and alcohol an equal volume]. After re- 
maining in this mixture for two weeks the pieces are trans- 
ferred to alcohol for two or three days, when they are ready 
for making sections. Double staining with the picric acid and 
hematoxylin, tinging with carmine, etc., will prepare the 
specimens for mounting in glycerine or dammar. 

The Ear. The following is Dr. Pritchard's method for 
preparing the cochlea. (Abbreviated from Beale. Mic. in 
Medicine, 4th ed. pp. 438, 439.) "The cochlea should be as 
fresh as possible. As much as possible of the bone around it 
should be removed. The membrane should be hardened by 
maceration in a % per cent, solution of chromic acid. From 
three weeks to a month will suffice in this mixture. The bone 
is softened by adding from a y 2 to a 1 per cent, solution of 
nitric acid to the chromic acid solution during the last few 
days of maceration. 

A large quantity of the solution should be used and it 
should be changed every four or five days. 

When the bone is quite soft it must be prepared for 
section in the following way : Make a small conical bag of 
paper, fill it with strong gum-water, and put in this softened 
cochlea (taken directly from the chromic acid solution,) leave 
it in the gum-water to soak for a few hours and then place the 
whole (paper bag and all) in alcohol. At the end of twenty- 
four hours remove the bag from the spirit, and pick away the 
paper and gum, which will then be quite white and hard. 
Should the cochlea now be found not sufficiently firm, it may 
be steeped in absolute alcohol for a minute or two and then it 
will be ready for section. 



THE STUDENTS MANUAL OF HISTOLOGY. 227 

For holding the cochlea in the microtome the following 
mixture is most convenient : 

Paraffine, ------ 5 parts. 

Spermaceti, ------ 2 parts. 

Lard, 1 part. 

Melt in a water bath. Before mounting dissolve away the 
gum with water and put up in glycerine or in a saturated so- 
lution of acetate of potash made with camphor water." 



CHAPTER XX. 



The Eye. 

THE posterior five-sixths of the eyeball presents a sphere 
on which rests the anterior one-sixth as a segment of a 
smaller sphere. The posterior sphere is opaque and is cover- 
ed with the sclerotic; the anterior sphere is transparent and 
covered with the cornea. 

The sclerotic is composed of dense fibrous tissue and 
varies in thickness in its different parts. At its anterior mar- 
gin where it joins the cornea it is about ^ of an inch thick ; 
over the greatest convexity of the eyeball -fo of an inch ; 
where it is pierced by the optic nerve -^ of an inch. It has 
few blood-vessels. On the inner surface of the sclerotic and 
uniting it with the choroid is a layer of connective tissue 
known as the " membrana fusca." It is continuous posteri- 
orly with the sheath of the optic nerve. 

The cornea is about -^ of an inch thick where it joins the 
sclerotic, but thinner in its central portion. Covering it on its 
free surface is a layer of pavement stratified epithelium. The 
superficial cells of this layer are flattened ; beneath these cells 
are smaller ones nearly round ; while beneath these there are 
cylindrical ones arranged perpendicular to the surface. These 
cells are all nucleated. Beneath this epithelial covering is a 
thin transparent membrane ''anterior elastic lamina,"— Bow- 
man's membrane. It is a continuation of the conjunctiva and 

is about g-oVo °f an i ncn m thickness. Covering the posterior 

228 



THE STUDENTS' MANUAL OF HISTOLOGY. 



229 



surface of the cornea is a single layer of polygonal nucleated 
cells. Anterior to this layer is a firm, elastic, transparent 
membrane, " membrane of Descemet or Demour." It varies 
in thickness from 30 1 00 to -g^Vo °f an mcn - The ligamentum 
iridis pectinatum is composed of processes from this membrane 
which have passed to the anterior surface of the iris. These 
processes are covered with epithelial cells which are continued 
directly from those on the posterior surface of the cornea. 




FIG. 157. Transverse section of tne eye. a, sclerotica. b, cornea. c, con- 
junctiva, d, circulus venosus iridis. e, choroid, with the pigment layer of the retina, 
f, ciliary muscle, g, ciliary process. h, iris. i, optic nerve. j, colliculus opticus. 
k, ora serrata retinae. I, crystalline lens. m, tunica Descemetii. n, membrana limi- 
tans interna of the retina. o, membrana hyaloidea. p, canalis Petiti. q, macula 
lutea. (Selected.) 

While these cells cover the processes they do not extend be- 
tween them, so that the anterior chamber is prolonged into the 
spaces between these processes. Other processes are given 
off to the sclerotic and choroid. At the margin of the sclerot- 



2 3 



THE STUDENTS MANUAL OF HISTOLOGY. 



ic, close to its junction with the cornea is a circular opening, 
the canal of Schlemm. Between the two transparent layers is 
the corneal tissue proper. This consists of pale bundles of 
fibres, which cross each other in every direction. The bundles 
of fibres may be divided into the most minute fibrillae. They 
become directly continuous with the fibres of the sclerotic and 
they cannot be separated from each other by maceration. 




FIG. 158. Vertical section of cornea of rabbit, hardened in chromic acid, a, an- 
terior layer of pavement epithelium, b, Substantia propria of the cornea, consisting of 
connective tissue fibres in more or less parallel bundles, between which are the cor- 
nea corpuscles. These, in vertical sections, appear spindle-shaped. c, the posterior 
lamina elastica, or Descemet's membrane, and the endothelium of polyhedral cells, d, 
which covers it. (Burdon-Sanderson.) 

These bundles of fibres are separated from each other by a 
ground, or interstitial substance. It is in these parts that the 
cell spaces are found. The spaces are flattened, stellate, and 
freely communicate with each other by their processes. When 
viewed in a vertical section they appear fusiform, but in a 
horizontal section they are flattened, irregularly stellate 



THE STUDENTS' MANUAL OF HISTOLOGY. 231 

spaces. Within these spaces are the corneal corpuscles ; they 
conform quite generally to the shape of the spaces, but do not 
completely fill them, thus leaving room for the lymph and the 
wandering cells. The cell substance is a clear protoplasm 
after the manner of that in the lacunae and canaliculi of bones, 
with a nucleus surrounded by granular matter. This proto- 
plasm entends out into the processes of the cell spaces, 
anastomosing with like processes from neighboring cells. 

The cell is capable of withdrawing and protruding these 
proce^-ses, the movements are slow, and are not to be taken 




FIG. 159. Corneal corpuscles of human cornea, silver staining, x 500. 

for the rapid amoeboid movements of the leucocytes. By the 
puncturing method the system of cell spaces, can be fully 
injected in the cornea and continued into the lymphatics of 
the sclerotic. Bowman's membrane is regarded by many as 
a part of the corneal tissue proper, but without corpuscles. 
The healthy cornea is not provided with blood-vessels, for 
these terminate in loops at the circumference. 



232 



THE STUDENTS MANUAL OF HISTOLOGY. 



The choroid is situated beneath the sclerotic and is at- 
tached to it by the membrana fusca. It is easily recognized 
by its dark color. It is about -fe of an inch thick near its an- 
terior termination which is very near the cornea ; here it ter- 
minates in a series of folds or plaits known as the ciliary pro- 
cesses. At its middle it is only y^- of an inch thick, but 
thicker again at its posterior. Its outer part consists of ar- 
teries and veins, arranged in a peculiar manner, described 
and illustrated in the standard works on anatomy. The veins 
are external to the arteries and are arranged in curves, vasa 
vorticosa. 




FIG. 160. 



Surface of the human iris. 
the pupil. 



a, the sphincter. 
(Iwanoff.) 



b, the dilator of 



Between the vessels are pigment cells with numerous fine 
branches. The outer part of this layer is surrounded by a 
membrane — lamina supra-choroidea. Between this membrane 
and the membrana fusca is a lymph space, which communi- 
cates with the space existing between the eyeball and the thin 
membrane surrounding it — the vaginalis oculi, — which is lined 
with a single layer of cells, affording a smooth surface for the 
eyeball to move against ; externally it separates the eyeball 
from the fat of the orbital cavity. The inner part of the 



THE STUDENTS MANUAL OF HISTOLOGY. 



233 



choroid consists of a layer of capillary vessels, the tunica 
Ruyschiana. Internal to this is the membrane of Bruch, a 
thin transparent membrane, exhibiting most minute folds or 
plaits at its anterior margin. The ciliary processes are folds or 
plaits of the choroid at its anterior extremity, projecting in- 
ternally. There are from fifty to seventy-five of them, and 
the largest are about -fa of an inch in length. Between these 
folds are smaller ones, formed by folds or plaits of the hyaloid 
membrane — the zone of Zinn 

The ciliary muscle surrounds the 
anterior margin of the choroid, 
arising by a thin tendon from the in- 
ner side of the boundary line be- 
tween the cornea and sclerotic. The 
fibres radiate posteriorly and are in- 
serted in the choroid, just outside of 
the ciliary processes. Some of the 
fibres pursue a circular course around 
the attachment of the iris ; this is 
the ring muscle of H. Miiller. It is 
much developed in hypermetropic 
eyes, being atrophied or absent in 
myopic eyes [Iwanoff.] The muscle 
is about -J- of an inch wide and -^ of 
an inch thick at its thickest part. 

The iris is the circular membrane 
just anterior to the crystalline lens. 
It gives the particular color to the 
eye, and with its perforated centre 
corresponds to the diaphragm of our optical instruments. It 
is about £ an inch across and is perforated a little to the nasal 
side of the centre. Although constantly varying in size, the 
pupil is ordinarily from -J- to £ of an inch across. At its peri- 




FIG. 161. Diagram of the 
connective substance of the 
retina. (Klein.) 



234 



THE STUDENTS MANUAL OF HISTOLOGY. 



phery it is connected with the choroid, cornea and ciliary 
muscle. The pupil is closed during a certain portion of fcetal 
life by a membrane called the pupillary membrane. It is not 
seen at an early period, but becomes most distinct at the sixth 
month, commences to break away at the seventh, and at birth 
no traces of it can be seen as a rule. The 
anterior surface of the iris is covered with 
a continuation of the epithelial cells that 
formed the posterior layer of the cornea. 
Just beneath this layer is a layer of irre- 
gular pigment cells. Covering the poster- 
ior surface is a layer of pigment cells also, 
a continuation of those, covering the retina 
and lining the ciliary processes. The cells 
are small, rich in pigment, and arranged 
in several layers. The color of black, 
brown, and gray eyes is caused by pig- 
ment cells in the substance of the iris it- 
self, while in blue eyes it arises from the 
posterior pigment cells showing through 
the nearly or quite colorless texture of the 
iris substance. Between the two epithelial 
layers is a quantity of non-striated muscle 
tissue, connective-tissue cells and fibres, 
and pigment cells of various shapes. Ar- 
ranged as a ring around the pupil is a 
layer of this muscle tissue about ^ of an 
inch in width. It is the constrictor, or 
sphinctor of the pupil. Other muscle fibres commence at the 
periphery aud converge toward the pupil, — the dilator of the 
pupil. The iris is very vascular, and well supplied with 
nerves from the 5th cranial and from the ophthalmic gang- 
lion. They follow the course of the blood-vessels and form a 



FIG. 162. "Nervous ele- 
ments of the retina. 

(Schultze.) 



fine plexus at the margins of the pupil. 



THE STUDENTS MANUAL OF HISTOLOGY. 



235 




The retina presents an ex- 
treme delicacy and a most com- 
plicated structure. It extends 
anteriorly to within ^ of an 
inch behind the ciliary proces- 
ses where it terminates in a 
serrated border — the ora ser- 
rata. Near the optic nerve it 
is about -gtg- of an inch thick, 
near the middle r ^ of an inch, 
and near its anterior edge -%^ 
of an inch. At the entrance of 
the optic nerve is a round disc, 
porus opticus. It forms a 
rounded elevation on the inner 
surface of this membrane, 
pierced in its centre for the 
passage of the vessels of the re- 
tina. This papilla is known as 
the colliculus nervi opticus. It 
is about 1 of an inch within, 
and rfg of an inch below the 
antero-posterior axis of the eve- 
ball. In the direct axis of the 
eye is a somewhat elliptical de- 
pression of a yellowish color 
and called the macula lutea. 
In the centre of this is a de- 
pression, the fovea centralis. 
The retina may be divided into 



FIG. 163. The nervous and epithelial a 9- 

mentsof the retina (semidiag'ammatic.) Quain 
fvf.er Schwalbe. 1, the layer of nerve fibres. 
2, the layer of nerve ce^ls. 3, the inner niolecu- 
ar layer. 4, the inner nuclear layer, s, the 
outer molecular layer. 6, the outer nuc I Ml .nor. 
7, the layer of rods and cones. 8, hexagonal pig- 
ment cells (not shown. 1 



-236 THE STUDENTS' MANUAL OF HISTOLOGY. 

eight layers, not counting the two limiting membranes which 
are more directly connected with the supporting connective- 
tissue frame-work. In a section made perpendicular to the 
surface, the retina presents an appearance represented in fig. 
162 from M. Schultze. The layers from without inwards are 
as follows : 

1. The iayer of pigment cells. 

2. The layer of rods and cones. 

3. Outer nuclear layer. 

4. Outer molecular layer. 

5. Inner nuclear layer. 

6. Inner molecular layer. 

7. Layer of nerve cells. 

8. Layer of nerve fibres. 

The cells of the first layer are hexagonal and were formerly 
-described as belonging to the choroid. That part of the cell 
towards the choroid is perfectly smooth while the part towards 
the rods and cones sends down numerous fine processes. 
These processes are filled with pigment granules, but they do 
not completely fill all the spaces between the rods and cones, 
for, according to Schwalbe, many of the spaces are filled with 
a liquid substance. The mass of the pigment granules is 
situated in the inner part of these cells ; the part next the 
choroid being nearly, if not entirely, free from them. 

The second layer is known as the stratum bacillosum and 
it represents the terminal cells of the optic nerve. 

It is composed of two elements, rods and cones. With 
one exception, to be described later, the rods are more numer- 
ous than the cones, the latter becoming less and less numerous 
as the periphery is approached. The rods are long cylinders, 
in length equal to the thickness of this layer and in diameter 
about the ytowo °f an i ncn - They are composed of two regu- 
lar parts, an outer and an inner segment. The outer segment 



THE STUDENTS' MANUAL OF HISTOLOGY. 



237 



refracts the light more strongly than the inner, which is paler 
and more granular. The former will not take staining, the 
latter stains readily with carmine, iodine, etc. The outer seg- 
ment breaks up into a number of superposed transversed 
discs only -§ - - } of an inch thick. On this segment can be 

seen a longitudinal striation, due 
to fine longitudinal grooves or de- 
pressions. This segment pene- 
trates into the pigmentary layer 
with a rounded point. Ritter says 
he has seen a primitive nerve 
fibrilla in the axis of the rods. At 
the outer border of the inner seg- 
ment, and forming a part of it, is 
a plano-convex body, the " lenti- 
form body," the "rod-ellipsoid" 
of Krause. The inner segment 
terminates below in a long, point- 
ed filament, a primitive nerve 
fibril. 

The cones are about one-half 
the length of the rods and are 
similar to them in structure. The 
outer segment is known as the 
"cone-rod," and it possesses in 
common with the rods a tendency to break up into transverse 
discs, although this tendency is not so great as in the rods. 
The inner segment or cone-body is like the rods, longitudinal- 
ly striated. In the cone-body a structure is found identical 
with the rod-ellipsoid of Krause. 

These appearances in both rods and cones are due prob- 
ably to this fact : the upper part only of the inner segment is 
longitudinally striated, for the lower part is homogenous. 





FIG. 164. Rods of the retina. From 
the monkey. A, rods, after maceration in 
iodized serum, the outer segment (b) 
truncated, the inner segment (a) coagu- 
lated, granular, and somewhat swollen. 
c, filament of the rods, d, nucleus. 
B, rods from the frog. 1 , fresh , magnified 
500 diameters. a, inner segment, b, 
outei segment, c, lentiform body, d, 
nucleus. 2, treated with dilute acetic 
acid and broken up into plates. 

(Schultze.) 



2 3 8 



THE STUDENTS MANUAL OF HISTOLOGY. 



In the case of the rods the fibrillated part of the inner 
segment occupies about the outer one-third, while in the cones 
it occupies as much as the outer two-thirds. The outer parts 
are strongly refractile, which fact does not appear to depend 
in the least on the degree of fibrillation of the segments, for 
sometimes the outer part of the inner segment of the cones 

appears entirely free from fibrils, yet 
it is easily distinguished by its great 
refracting power. 

The third layer consists of granules 
or nuclei in connection with the deli- 
cate prolongations of the rods and 
cones. The granules of the rods are 
swellings on the prolongations, one 
to each fibre. They are situated 
some distance from the bases of the 
rods, near the molecular layer. Each 
enlargement has a nucleus and is 
characterized, according to Henle, by 
a cross-striped appearance. The rod 
fibril prolonged from this granule is 
interrupted by numerous varicosities 
and finally terminates in a larger 
varicosity just before entering the 
molecular layer. The granules of 
the cones are not crossed by any 
bands. Each granule has a nucleus 
and nucleolus and the whole cone 
fibre is much larger than that of the 
rods. The fibre terminates below in 
an expanded extremity from which 
proceed numerous prolongations into 
the molecular layer. 




FIG. 165. Fibrillated coveringof 
the rods and cones. 1 , rods. 2, 
cones of man. a, outer, b, inner 
member, c, rod-filament, d, llmi- 
ians-externa. 3, rod of the sheep. 
The fibrillae project beyond the in- 
ner member. The outer member 
is wanting. (Schu)tze.) 



THE STUDENTS MANUAL OF HISTOLOGY. 239 

In the molecular layer little is to be recognized but a 
granular appearance, minute fibrillae and a few nuclei. 

The inner nuclear layer consists mainly of nucleus bodies, 
like those of the outer nuclear layer, only larger. 

In the layer of nerve cells are foand large multipolar cells 
resembling those found in the brain. They measure from the 
g/oo to the yj-g- part of an inch in diameter. Each cell has an 
unbranched process, axis cylinder, which passes inwards 
among the fibres of the inner layer, with one of which it doubt- 
less becomes continuous. The branched processes extend into 
the outer layer and are soon lost in its substance. As a rule 
they exist in a single layer, but near the yellow spot they are 
from five to ten layers deep. The eighth layer is composed of 
the most minute nerve fibrils varying from g 0000 to K |^ f part 
of an inch in diameter. The delicate structures of the retina 
are held in place by a system of connective-tissue fibres, the 
" supporting fibres of Miiller." These fibres commence just 
beneath the inner retinal layer, where by connected bases they 
torm a boundary line, — the membrana limitans interna. The 
fibres then pass through the several layers, as illustrated in the 
figure, until they reach the bases of the rods and cones, where 
they form a boundary line also, — the membrana limitans ex- 
terna. From here branches pass between the rods and cones 
and invest their bases. 

MACULA LUTEA. 

The macula lutea is an oval spot about ^V of an inch in 
its horizontal diameter. Its yellow color is due to the presence 
of a peculiar yellow pigment, which is not deposited in grains. 
It is a diffuse hyaline coloring matter, soluble in water or alco- 
hol. The macula lutea presents the following histological 
peculiarities : 

1. The layer of nerve fibres is wanting. 



240 



THE STUDENTS MANUAL OF HISTOLOGY. 



2. The layer of ganglionic nerve cells is increased from 
a single layer to six or eight layers ; when they reach the 
fovea centralis they are entirely absent. 

3. Several of the remaining layers diminish in thickness 
as they approach the yellow spot and disappear at the fovea 

centralis. 

4. As a result of these 
changes only two layers remain 
at the central depression, the 
outer nuclear layer and the 
layer of rods and cones. Even 
these exhibit peculiarities. 

5. The fibres with which the 
nuclei of the third layer are 
connected, are arranged in an 
oblique direction, reducing the 
layer much in thickness. At 
the borders of the macula lutea 
the cones are separated from 
each other by a single layer of 
rods, while in the fovea cen- 
tralis the rods are altogether 
absent. Here the cones are 
longer and more slender than 
elsewhere. 




FIG. 166. Diagrammatic section of human 
retina through the macula lutea and fovea cen- 
tralis. I, internal surface of the retina, in contact 
with the vitreous body. 2, ganglionic layer of 
nerve cells. 3, intermediate layers of the retina, 
disappearing at the centre of the macula lutea. 
4, layer of nuclei, showing the oblique course of 
the fibres in this region. 5, layer of rods and 
ccoes, consisting at its central portion exclusively 
of. attenuated and elongated cones. 6, external 
surface of the retina, in contact with the choroid. 
In the middle of the diagram is the depression of 
the fovea centralis. (Schultze.) 



THE STUDENTS MANUAL OF HISTOLOGY. 24I 

VITREOUS HUMOR. 

The vitreous humor occupies about four-fifths of the eye- 
ball and is of a soft gelatinous consistence. A concavity exists 
in its forepart for the reception of the lens and its capsule. 
When treated with certain reagents it has the appearance of 
being composed of distinct membranes, arranged concentric- 
ally, and between these membranes there is a fluid substance. 
A radial striation has been observed in the human vitreous 
body. Very nearly in the antero-posterior axis of the eye is a 
canal, lined with a distinct membrane and filled with a fluid ; 
it extends from the optic nerve to the posterior capsule of the 
lens. This is the " canal of Stilling." In the vitreous body 
are corpuscles resembling white blood-cor- 
puscles. 

The hyaloid membrane is an exceed- 
ingly delicate membrane, measuring about 
-jtsVo of an inch in thickness. It is in con- 
tact with the retina externally and with the 
vitreous body internally. When near the 

FIG. 167. The rod layer . ...... 

seen from without, a, cones, ciliary processes it divides into two parts. 

b, cone rods. c, ordinary „. . . 

rods. 1, from the macula lu- 1 he posterior portion lines the concavity 

tea. 2, at the margin of the , r r , . , 

same. 3, from the centre of in the lorepart or the vitreous body. The 

the retina. (Helmholtz.) . , . . . . , __, 

v anterior divides into two parts, i. The 

anterior of these parts is known as the zone of Zinn ; it ter- 
minates in the anterior capsule of the lens, and it is thrown 
into folds or plaits that correspond with the folds of the ciliary 
processes into which they fit closely. 2. The posterior of 
these parts is very thin and is attached to the posterior capsule 
of the lens. These two parts by their division enclose a tri- 
angular space, called the " canal of Petit." After death this 
canal is found filled with a serous fluid. 

THE LENS. 

The lens is a transparent bi-convex body placed directly 




242 



THE STUDENTS MANUAL OF HISTOLOGY. 



behind the pupil. It is completely surrounded by a thin mem- 
brane, the capsule of the lens, — which is lined with a layer of 
delicate cells. 

The lens is about one-third of an inch in its transverse, 
and one- fifth of an inch in its antero-posterior diameters. Its 
posterior surface is more convex than its anterior. When 
viewed with a low power the lens presents a star with from 
nine to sixteen radiations. In the foetus there are but three 
radiations upon either surface. The rays of the stars of one 
side are situated between the rays of the other side. The 
outer portions of a fresh lens are much softer than the inner 
portions and they are easily detached from them ; the hard 
centre is known as the nucleus of the lens. The lens is com- 
posed of a great number of six sided prisms arranged closely 
together with but little intervening cement-substance. These 

fibres are about the 
of an inch broad and 




rrVo- of 



their 
edges are many times quite 
regularly dentated. They 
pass in a curved direction 
from the centre and from 
the rays of the star to the 
periphery where they turn 
and pass over to the other 
side to its star. 

The fibres of the super- 
ew of the fibres of ficial layers have an oval nu- 

the lens from the ox, showing the serrated edges. „i_„„ „„A ^~~,~<.:~,~~ ~ 

(Quain., B, transverse section of the fibres of the GleUS and SOmetimeS a nU- 
lens from the human eye. (Kolliker.) deoluS, proving that all the 

fibres of the lens must be regarded as elongated cells. 

In the more internal parts of the lens the nuclei are absent 
and the fibres are harder. The capsule of the lens is a very 
thin, transparent membrane, about SQ * 00 of an inch thick at 




longitudinal 



THE STUDENTS MANUAL OF HISTOLOGY. 



243 



its centre and so elastic that when ruptured it will frequently 
contract with sufficient force to expel the lens body. It is 
lined anteriorly with a layer of nucleated polygonal cells aver- 
aging y-gVo °f an * ncn m diameter. No such cells line the 
posterior part. 

METHODS OF EXAMINING. 

To understand the relations of the 
different parts to each other, sections of 
the whole eye should be made by the 
aid of the freezing microtome. 

The cornea may be studied in many 
different ways. The different layers 
should be examined first. For this pur- 
pose the cornea is removed from the 
eye of an ox and placed at once in 
Miiller's fluid where it is allowed to re- 
main for two weeks, when it is trans- 
ferred to alcohol. In two or three days 
sections can be made vertical to the 
surface, stained in hematoxylin, cleared 
in oil of cloves and mounted in dam- 
mar. To see the branching and anasto- 
mosing connective-tissue corpuscles the 
cornea is placed in a .-|- per cent, chloride 
of gold solution until the tissue is of a 
pale, yellow color ; after washing it is 
transferred into water slightly acidulated 
with acetic acid. Upon exposure to 
light the specimen turns to a violet 
color when it is examined with a high 
power. If the epithelial cells render the 
ma^?noMt^i?s n ^rshow e specimen indistinct they are removed 
ir^l^^^uch!^ b y brushin S or scraping. After the 



244 THE STUDENT S MANUAL OF HISTOLOGY. 

gold staining the corneal corpuscles may be isolated. For this 
purpose a 25 per cent, solution of sodic hydrate is used : this 
destroys the intermediate substance before it does the cor- 
puscles. The cornea, deprived of its epithelium is placed in 
this solution for 30 or 40 minutes, when the alkali is replaced 
by water, to which has been added a few drops of acetic acid. 
If portions of this membrane be examined in glycerine the cor- 
puscles will be displayed beautifully ; the delicate nerve fibrils 
and the anastomosing branches of the cells will be clearly 
brought out. 

Nitrate of silver staining can be employed and the tissue 
treated as usual in such cases. 

To examine the retina an unopened eyeball is placed in 
Miiller's fluid for two weeks and then transferred to alcohol 
for a few days. Sections of the retina made vertical to the 
surface can b*e examined in glycerine or first stained slightly 
with carmine. Sections should be examined from different 
parts of the retina when the local changes will be made ap- 
parent. 

Sections should be made from a retina hardened in osmic 
acid. For this purpose small pieces are removed as carefully 
as possible and placed in a 2 per cent, solution of this acid. 
Here they should remain for six or eight hours, when they 
should be washed thoroughly in water, stained with hsematoxy- 
lin, embedded, sections cut and examined. 

To macerate the retina and thus procure its elements in 
an isolated condition several reagents are employed. Notably 
the 2 per cent, osmic acid solution. After remaining in this 
solution for six or eight hours a piece of the retina is trans- 
ferred to a glass slide and by the aid of needles carefully 
teased in dilute glycerine ; or the acid may be reduced one- 
half and the tissue allowed to remain in it 24 hours. The 
retina is suitable for teasing just after removal from Miiller's 
fluid. 



THE STUDENTS MANUAL OF HISTOLOGY. 245 

The retina in the fresh condition should be examined. 
As soon as removed from the eye a piece of it is teased with 
needles in a drop of the aqueous humor, covered, and 
examined with a high power. 

The lens is hardened in Midler's fluid and alcohol for ob- 
taining sections. To isolate the fibres it is boiled for ten 
minutes in a i per cent, solution of sulphuric acid and then 
teased in glycerine. If too transparent slight tingeing with 
aniline blue will be suitable. Many times very instructive 
sections are obtained from a lens that has been exposed to 
the air on a glass slide for a day or two. It has acquired such 
a degree of consistence that sections can be cut conveniently 
in the direction to show the delicate hexagonal cut ends of the 
lens fibres. Other parts of the eye should be hardened in 
Miiller's fluid and alcohol for examination ; sections made 
and stained as with the simpler tissues. 

To study the vascular arrangement, the eye of an ox is 
carefully removed from its bony socket and injected from the 
artery with the Prussian blue. 

For general purposes of study the human eye is preferred 
if it can be obtained perfectly healthy and in a fresh condition. 
If not, the eyes of the pig, albino rabbit and ox will be found 
very suitable. 



CHAPTER XXI. 



Tumors. 

HYPERTROPHY may be defined to be an increased nu- 
tritive activity of a part. It may be either simple or 
numerical. By simple hypertrophy is understood an enlarge- 
ment of a part by the increase in size of its anatomical ele- 
ments. In numerical hypertrophy the enlargement takes place 
through an increase in the number of cells. These are gener- 
ally associated. 

Hypertrophy is most frequently met with in the muscular 
system where it is often conservative in nature, as when the 
walls of the bladder are increased in thickness to give addition- 
al power to overcome some obstruction at its base, e. g. en- 
larged prostate, etc, or when the walls of the intestine become 
thickened above a point of obstruction, or when the gastroc- 
nemei become largely developed in the ballet dancer to over- 
come the extra strain put upon them. This increased activity 
may give rise to entirely new elements — to new formations. 
The inflammatory new formations are very unstable and when 
their cause, usually some irritation, is removed, they will have 
a strong tendency to return to a healthy standard or condition. 
The non-inflammatory have great independence, grow by an 
inherent activity of their own, and are constantly tending to 
become removed farther and farther from a healthy condition. 
Their general tendency is to increase in size, although after a 

246 



THE STUDENTS MANUAL OF HISTOLOGY. 



2 47 



time they may remain permanent. To this class belong the 
new formations, known as tumors. A tumor is many times 
pathological simply because its specific elements occur in a 
place where they do not normally belong. Virchow calls a tu- 
mor composed of but one tissue "histioid," when composed of 
several tissues "organoid." When in addition to the latter 
there are organ-like tissues " systematoid." 

If a new formation occurs in a tissue agreeing with it in 
structure it is said to be "homologous." If unlike it, it is 
"heterologous." 

All of the pathological elements found in a new formation, 
including the cells, nuclei, matrix, vessels, etc., are prototypes 
of those found in the normal tissues, only undergoing change 
and destruction more readily. 

The cells of these growths are reproduced most frequent- 
ly by cell division, the nucleus dividing first, followed by a 
division of the formed part of the cell. This has been ob- 
served to occur in a very few seconds. Sometimes the nucleus 
alone will divide, these nuclei thus formed dividing again and 
again, until one cell may possess in this way from four to 
twenty or more nuclei. 

These cells are known as the " giant," '" mother," or "mye- 
loid" cells. They are found normally in the medullary sub- 
stance of bone. 

Pathological cells then come from pre-existing cells, and 
when newly formed are usually small and round, having a nu- 
cleus and also nucleolus, or composed of nucleus matter alone, 
simple undifferentiated protoplasmic cells. At this stage it 
would be impossible to tell the future of the growth. Like the 
small cells of the embryo, they are entirely undifferentiated. 
These cells may be the round cells of a sarcoma or the cells of 
connective tissue. 

As soOn as a tumor is completely developed it is liable soon* 
er or later to undergo some of the forms of degeneration. It" it 



248 THE STUDENTS' MANUAL OF HISTOLOGY. 

has been of short duration, attained a considerable size, and if it 
is composed largely of cells, then it will undergo these changes 
all the more rapidly. If it has been of slow growth and its 
elements are developed into tissue, then it will not be liable to 
degenerate. Fatty degeneration is most commonly met with. 
This is probably due to the fact that in the rapid formation of 
new tissue there is not a proportionately new formation of 
blood-vessels, and as a result of the insufficient circulation and 
want of nutritive material, the fatty metamorphosis occurs. 

Tumors may also undergo pigmentary degeneration, usu- 
ally from a deposit of melanin. This is a black, or nearly 
black, substance found physiologically in the skin and eye. It 
is seen either as free granules in the tumor or deposited in the 
cells. It does not appear to be at all susceptible to reagents, 
and its origin is probably the same as that of haematoidin. In 
caseation the fluids are absorbed and the elements are dried 
up, changed into a yellowish cheesy material, which process 
may continue until the whole mass may become surrounded by 
a capsule of fibrous tissue. In calcification, small calcareous 
particles are infiltrated through the mass. Sometimes soften- 
ing liquefies the whole mass into a thin liquid, which under the 
microscope is seen to consist of broken down material, granu- 
lar matter, fat, etc. 

Colloid and mucoid degenerations also occur when the al- 
buminous ingredients are transformed into substances chemi- 
cally resembling mucin and an allied colloid material. 

A tumor is malignant when it has a tendency to recur in 
the same or some distant place after its removal. 

It is innocent when this tendency is not present. The 
term "malignancy" then, is purely a clinical one and does not 
refer to any property of the growth to destroy life. The 
heterologous character of a growth is an evidence of its malig- 
nancy. 

In the examination of tumors the fresh cut surface should 



THE STUDENTS MANUAL OF HISTOLOGY. 249 

be scraped and this examined for cells, their shape, number, 
size, nuclei, the size and number of nuclei in each cell, all 
should be carefully noted. Then the tumor should be cut in 
small pieces not over one-half an inch square and placed at 
once in dilute alcohol, to be replaced in a few days by common 
methylic alcohol, and if the tissue still remains too soft for 
cutting thin sections, stronger alcohol may be added for 
a day or two. Mliller's fluid may be employed, but at this 
laboratory the best results have been obtained by the use of 
alcohol alone. In two weeks the tissue will be of sufficient 
consistence to allow thin sections to be made with the aid of a 
razor. By holding the piece of tissue firmly between the 
thumb and fingers of the left hand, the razor held in the 
right hand can be drawn from heel to point over the tissue 
cutting the section sufficiently thin for examination. Or 
by using one of the embedding mixtures already given 
the piece may be embedded in the microtome and sections 
cut as has been described. The arrangement of the fibres 
and cells should be noticed together with any alveolar stroma 
that may be present. 

Carmine and hematoxylin are useful staining agents. 

If it is desired to secure the specimen permanently it 
should be cleared in the oil of cloves and mounted in dammar. 

It is very difficult to make a satisfactory classification of 
the new formations. The classification given in T. Henry 
Green's " Pathology and Morbid Anatomy" is as free from ob- 
jections as any with which we are acquainted. It is here given 
with slight changes : 

CLASSIFICATION OF TUMORS. 

I. Type of the fully developed connective tissues. 
Type of fibrous tissue, - - - Fibroma. 
Type of adipose tissue, - - - Lipoma. 



250 THE STUDENTS MANUAL OF HISTOLOGY. 

Type of cartilage tissue, - - - Enchondroma. 

Type of bone tissue, - - - - Osteoma. 

Type of mucous tissue, - - - Myxoma. 

Type of lymphatics, - - - - Lymphoma. 

II. Type of higher tissues. 

Type of muscle, Myoma. 

Type of nerve, ------- Neuroma. 

Type of blood-vessels, - - Angioma. 

Type of papillae, Papilloma. 

Type of secreting glands, - - Adenoma. 

III. Type of embryonic tissue. — The sarcomata. 

Spindle-celled sarcoma. 
Round-celled sarcoma. 
Myeloid sarcoma. 

IV. The carcinomata. 

Scirrhus. 
Encephaloid. 
Colloid. 
Epithelioma. 

FULLY DEVELOPED CONNECTIVE TISSUE. 

Of the two kinds of corpuscles found in connective tissue, 
the movable or wandering kind is the most important in this 
connection. In size, contractility, ability to wander, etc., they 
seem identical with the white blood corpuscles and pus cor- 
puscles. In all probability they have their origin in the blood. 
It is not known whether they can pass into the regular connec- 
tive-tissue corpuscle or not. Neither is it known in what 
channel they move. 

TYPE OF FIBROUS TISSUE. 

Fibroma, fibroid or connective-tissue tumor. This tumor 
consists of quite distinct fibres that are without any arrange- 
ment, and separated only with difficulty. If the ' section be 
made across a blood-vessel the fibres will be seen running a cir- 




THE STUDENTS MANUAL OF HISTOLOGY. 251 

cular manner around it, as seen at the left upper corner of 
figure 170. Only a few cells will be found, and these are most 
abundant in the neighborhood of blood-vessels. They are 

usually of the spindle-shaped or 
stellate variety. Nuclei that 
take the staining readily are seen 
distributed over the field. As a 
rule there are but few blood- 
vessels, but it sometimes occurs 
that the walls of the vessels have 
become firmly united with the 
structure of the tumor, hence if 
the growth be cut into or injured 
severely the mouths of the vessels 
will not be able to contract and 
fig. 170. Fibroma. profuse hemorrhage results. 

In size the fibromata vary from a very small circumfer- 
ence to an immense growth. Their form is also varying. The 
fresh cut surface is usually dry, only in the rapidly growing 
younger growths when a serous or mucous fluid exudes. 
Arising from the skin they are usually softer and less dense 
than those found in other parts, and in this situation are usu- 
ally single. They are generally limited by a capsule and have 
a slow growth, occurring in middle and advanced life. They 
increase in size by a central growth, by a multiplication of 
their own elements, and do not invade the surrounding healthy 
structure. 

They are then innocent growths and cause disturbance to 
the organ or tissue in which they are situated and to the 
whole organism only from their size. The fibromata are not 
liable to undergo degeneration. Fatty degeneration, calcifica- 
tion, mucoid softenings and hemorrhages are met with usually 
affecting only a part of the growth. Growing beneath the 
skin these tumors ^re sometimes soft, without a capsule and 



252 THE STUDENTS MANUAL OF HISTOLOGY. 

multiple. They are known here as wens. Nasal polypi are a 
variety. So is a tumor often described as a neuroma, which 
under the microscope is seen not to consist of true nerve 
tissue, but is fibrous. These growths usually commence from 
the connective-tissue surrounding the nerve, the neurilemma, 
and by increasing in size, either press upon the nerve proper 
or grow around it and thus as they increase in size they com- 
press the nerve. They are generally small, round, hard 
tumors that are painful in the extreme. Uterine fibroids are 
rarely composed of fibrous tissue. They will be described 
under muscular tumors. The fibromata are frequently com- 
bined with other forms. 

TYPE OF ADIPOSE TISSUE. 

In structure a lipoma resembles ordinary adipose tissue, 
consisting of large cells that are fully distended with fat. The 
nuclei of the cells are not visible unless the fat be dissolved 
from the cells, or unless a cell is found containing but very 
little fat. They vary in size, frequently attaining a most enor- 
mous growth. The fresh cut surface shows fatty tissue. It 
occurs most frequently in parts where fat normally exists, 
rarely in other parts, is usually sharply circumscribed, encap- 
suled, grows slowly and with a central growth. It has no ten- 
dency to return after removal. 

It rarely undergoes any of the degen- 
erations and when occurring only small 
parts are affected. Figure 1 7 1 shows a 
thin section of this tumor with the inter- 
cellular connective-tissue. 

TYPE OF CARTILAGE. 

Enchondroma, chondroma. This tu- 
mor is rarely found composed of cartilagin- 
Lipoma. ous tissue alone but usually combined 




THE STUDENTS MANUAL OF HISTOLOGY. 253 

with connective tissue. It may be either hyaline, reticular or 
fibrous cartilage, or all three combined. The number and 
size are very variable. Some are spindle-shaped, some stel- 
late and movable. Usually, however, they resemble the cells 
of normal cartilage. The enchondromata vary in size, are 
usually single, occasionally multiple. They occur in the early 
part of life, even in the new born. By far the greater number 
affect the bones and most frequently the medulla. Thus the 
articulating surfaces are rarely affected. They may arise 
from cartilage itself, their likeness to normal cartilage is then 
more exact. In some of the softer forms there is a tendency 
to return after removal, affecting even the lymphatics, and in 
the young causing cachexia. The malignant properties of the 
enchondromata, when present, are probably due to the fact 
that sarcomatous elements are associated with them. How- 
ever healing almost invariably occurs after complete extirpa- 
tion, and in the case of a pure enchondroma malignancy 
may be said to be entirely absent. Of the many degenera- 
tions to which this tumor is subject calcification is the most 
common. Ossification sometimes affects the periphery of the 
growth so that it is surrounded by a thin bony wall. Spicule 
of bone are frequently found through the growth. A speci- 
men in the author's possession shows about one-third of the 
growth truely ossified, the remainder resembling normal carti- 
lage. The line between the two being sharp and distinct. 

For an illustration of this kind of growth see cartilage. 

TYPE OF BONY STRUCTURE. 

Osseous tumor, Osteoma. In the case of this tumor the 
bony appearance is the natural result of development, whereas 
in many other cases — tumors having undergone osseous de- 
generation — it is accidental. It has an independent growth 
and is not to be confounded with the products of Inflammation 



254 



THE STUDENTS MANUAL OF HISTOLOGY. 



of bone, as the callus after fractures, etc. Most of the osteo- 
mata arise from connective-tissue. They may have their 
origin from cartilage bone, or the periosteum of bone. Those 
having their origin apart from bone, heterologous, are known as 
osteophytes. They are found near diseased joints, near the 
seat of inflammatory processes and in many other situations. 
They are found not uncommonly in the lungs and brain. 
They are to be carefully distinguished from growths that have 
become partly ossified, for in the latter case they might be 
more or less malignant, while a true osteoma is perfectly inno- 
cent. The homologous exostoses are found most frequently 
on the external and internal surfaces of the skull, in the orbit, 
on the upper and lower jaw, etc. They are troublesome only 
when some neighboring part is affected by pressure. The 
appearance under the microscope is not unlike that of the true 
bone, at least the lacunae and canaliculi, are present, although 
not arranged in any order. 

TYPE OF MUCOUS TISSUE. 

Myxoma, mucous tumor, tumor mucosus, gelatiniform or 
colloid sarcoma. A myxoma con- 
sists, of a mucous basis substance in 
which are spindle-shaped or stellate 
cells which anastomose with each 
other. Some of these cells are 
shown in figure 172. A few are 
round or oval or spherical. This is 
very generally the case in the 
younger growths. If young and 
rapidly growing the number of these cells will be largely in- 
creased proportionately. A nucleus is seen in each of the cells. 
Sometimes two nuclei are present. The refracting power of 
the mucus is so great that some care is necessary in order to 
see the outlines of the cells. Staining will be of advantage 




FIG. 172. Myxoma. 



THE STUDENTS MANUAL OF HISTOLOGY. 255 

here. The cells are easily obtained by simply scraping the cut 
surface and adding a little saline solution to the scrapings. 
They are closely related to cells found in the sarcomata, and 
by many are so classed. The same kind of tissue exists in two 
places in the body physiologically, in the vitreous humor of the 
eye and in the umbilical cord. 

The myxomata usually occur as single tumors, and are 
generally round, uniform and small. The fresh cut surface 
may show septa of connective tissue, giving the growth a soft 
but quite firm consistence, or the connective tissue may be 
nearly, if not entirely absent. There will then escape a viscid 
mass of mucilagenous consistence to .such a degree that the 
whole tumor will become flattened and formless. Their most 
favorite seat is in the adipose tissues and they are here gener- 
ally encapsuled. Their growth is usually slow although they 
are many times of extraordinary size. The walls of the blood- 
vessels are very thin and liable to rupture. Hence the fre- 
quency with which sanguineous cysts are met with. 

The cells themselves may become destroyed by either 
fatty or mucoid degeneration. As a rule the myxomata are 

innocent growths. Sometimes, 
however, they exhibit malignant 
properties. This probably is due 
to the fact that many times these 
growths are combined with others, 
especially the sarcomata. Figure 
172 represents some of the cells 
of a myxoma removed from the 
fig. .73. Lymphoma. vagina. The growth was about 

the size of a walnut. 

TYPE OF LYMPHATIC TISSUE. 

Lymphoma, Lymphadenoma. Figure 173 represents a 
section of a lymphoma of the arm. It is not very unlike a 




256 THE STUDENTS' MANUAL OF HISTOLOGY. 

lymphatic gland in structure, consisting of a basis of distinct 
fibres which branch and cross each other like a net-work, and 
of cells identical with the white blood corpuscles. These cells 
fill up the space in the basis, but in the figure they have been 
nearly all removed by brushing the section with a camel's hair 
brush moistened in water. The firmness of the tumor will de- 
pend upon the comparative amount of basis fibres and nu- 
cleated cells. If the growth is young and increasing rapidly 
in size then the cells will be the more prominent part of the 
growth. Later the number will diminish and the reticulum 
become thicker and firmer. These tumors not infrequently ac- 
quire a large growth even infiltrating the surrounding tissues. 
They are homologous primarily and become heterologous only 
from the new tissue extending into surrounding parts, or from 
their growing in a place where the lymphatics are very small 
and few in number. 

The lymphomata are innocent growths and are not liable 
to undergo degenerative changes. In the disease known as 
"Hodgkin's disease" the new growths in various parts of the 
body are like the one described. The enlargement of the 
spleen in leukaemia is of the same nature. 

TYPE OF MUSCULAR TISSUE. 

Myoma. A tumor composed of striated muscle is one of 
the rarest of the new formations. A myoma composed of 
smooth or non-striated muscle is most frequently met with in 
the uterus, where it is generally known as a "uterine fibroid," 
and when projecting into the cavity of the uterus or extending 
by a pedicle out of the neck is called a "uterine polypus." 
The muscle cells form one but not the only element. Connec- 
tive tissue may exist in great abundance. This is especially 
the case in the older growths. In the new growths it is not 
uncommon to find almost exclusively the characteristic non- 
striated muscle cells. There are few blood-vessels distributed 



THE STUDENTS MANUAL OF HISTOLOGY. 257 



through the connective tissue. These are homologous 
growths, of slow growth, usually single, but often multiple. 
They are liable to undergo softening, or more freqently to be- 
come calcified. They are perfectly innocent, exhibiting no 
tendency to return after removal. 

TYPE OF NERVOUS TISSUE. 

Neuroma. These consist of true nerve fibres and are not 
the growths so commonly met with growing from the sheath of 
nerves or within the sheath. They are composed of ordinary 
medullated nerve fibres associated with connective tissue. 
They are found on the ends of divided nerves, growing after 
amputations. They are usually very small nodules, innocent, 
and are remarkable largely for the great pain they cause. 

TYPE OF BLOOD-VESSELS. 

Angioma. These tumors are composed of blood-vessels 
held together by connective tissue. The diagnosis is readily 
made without the aid of the microscope. 

TYPE OF PAPILLA. 

Papilloma, papillary or villous tumor. This tumor con- 
sists of a body of connective tissue with a covering of epitheli- 
al cells, resembling the papillae of the skin. They are rarely 
without blood-vessels which end either in a capillary net-work 
work or in single loop. Cells may be seen scattered through 
the connective-tissue basis. The epithelial covering is gener- 
ally like that from which the part arises. The papillomata 
may occur on any surface of the body, but more generally 
where papilloe and villi normally exist. They occur singly or 
many papilloe may be affected giving the growth a cauliflower 
•appearance. The papillomata exhibit no tendency to return 
after removal, yet in many ways they may become serious 
troubles. They are liable to undergo ulceration, followed by 



25» 



THE STUDENTS' MANUAL OF HISTOLOGY. 



hemorrhage, especially when situated in the bladder and in- 
testine. Warts of the skin, common warts and horny growths 
are varieties of this class, so also are the condylomata and 

venerial warts. Figure 174 rep- 
resents a growth of this character. 
This will not be mistaken for 
epithelioma, for in the case 
of a papilloma, the epithelial 
cells are in their normal relations 
to the part, they are homologous, 
while in an epithelioma the cells 
are heterologous. 

TYPE OF GLAND TISSUE. 

Adenoma, glandular tumor. In 
structure an adenoma is like that 
tissue in which it is found, or 
from which it originated, for it 
may after a time become com- 
pletely separated from the old 
gland. Its function will not be like the normal gland how- 
ever. Indeed it can be said to have no function whatever. 
The adenomata are very difficult tumors to diagnose, being 
very liable to undergo the degenerations, especially the forma- 
tion of cysts and the changing into calcareous forms. They 
are frequently, perhaps most frequently, found in the female 
mammae. They are very commonly associated with other 
forms as adeno-sarcoma, adeno-myxoma, etc. In the 
mammary gland an adenoma is most frequently associated 
with a fibroma, giving rise to the familiar adeno-fibroma. 
Here the aceni of the gland are separated from each other by 
a large growth of fibrous tissue between them, or a bundle of 
aceni may be separated from another bundle by an hyper- 
trophy of the intervening connective tissue. This may de- 




ne 174. Papilloma. 



THE STUPENTS MANUAL OF HISTOLOGY. 



259 



velop to such an extent that the secreting tubes of the gland 
will be nearly obliterated. Figure 175 represents the aceni of 
the gland widely separated from each other. 

fU)!^\v\. The growth of these tumors 

is usually slow. While they 
are primarily innocent they 
may assume malignant proper- 
ties. 

TYPE OF EMBRYONIC TISSUES, 
THE SARCOMATA. 

Fibro-cellular, fibro- plastic, 
fibro-nucleated, recurrent fib- 
roid, myeloid. The sarcomata 
are divided into varieties ac- 
cording to the majority of their 
cells. The spindle-celled sar- 
coma is composed almost en- 
tirely of long fusiform, com- 
paratively thick-bodied, n u - 
cleated cells. The processes 
from either end of the cell are 

usually long and not infrequently branched. Each cell 

is possessed with one nucleus frequently with two nuclei. 

This variety is the most common of this large class of new- 
formations. Figure 176 represents some 

of these cells taken from the leg of a man. 

The leg had been diseased nearly two 

years. A majority of the cells were large, 

the nucleus multiple in many cells, and a 

number of free nuclei or small round cells 

were in the field also. The disease had J*j^>JJK£j 

affected the tibia to its very centre, so that 




fig. .75. 

gland. 



Adeno-fibroma, from mammary 




260 



THE STUDENTS MANUAL OF HISTOLOGY 




FIG .77- 
tibia. 



Myeloid cells, from sarcoma of 



deep in the growth were found the myeloid cells, seen at 
figure 177. The spindle-shaped cells vary much in size, both 
in the same growth and also in different growths. Some 
growths will be composed almost entirely of cells averaging 

Y^Vo °f an ' * ncn length) while 
others of much larger cells, of 
twice the size, with larger nu- 
clei, and some growths combine 
the two. The cells are many 
times arranged close together, 
so that there is scarcely any 
space between them, giving but 
a small quantity of intercellular 
substance, which in turn may 
be either fluid, or granular, or firm and fibrillated. Large 
cells, large nuclei, and the presence in a cell of more than one 
nucleus, are evidences of a high degree of malignancy. The 
cells are not infrequently arranged parallel to each other, 
running in bundles all through the growth, giving it very 
much the appearance of a fibroma. This tumor arises as do 
all the sarcomata, from pre-existing connective tissue, and in- 
creases, either by multiplication of its own elements (central 
growth), or by continually invading the healthy tissue arovmd 
it (peripheral growth), which is highly characteristic of all 
this class. The sarcomata are usually quite vascular, the walls 
of the blood-vessels being composed of embryonic tissue, ren- 
der them exceedingly liable to rupture, causing the formation 
of sanguineous cysts, severe hemorrhage, etc. They are also 
very liable to undergo fatty degeneration. Although this va- 
riety may become encapsuled, it possesses unmistakable malig- 
nant properties. The growth is usually rapid. 

Figure 178 represents the cells from a melanotic sarcoma 
of the eye. This tumor extended into the vitreous humor 
from the choroid, was globular in shape and a trifle over one- 



THE STUDENTS MANUAL OF HISTOLOGY. 



261 




half an inch in diameter. These cells are mostly spindle- 
shaped and nucleated, but they now contain a large amount of 
dark colored pigment melanin, rendering the nuclei obscure, 
and many times invisible. The large majority of these 

growths is found primarily in the 
eye, where this pigment normally 
exists. They may arise from the 
superficial integument. Some- 
times this pigment will be de- 
posited only in a slight degree, 
giving the growth a brownish ap- 
fig. .78. Melanotic ceils, from sar- pearance. Then too, only a few 

coma of choroid. of ^ cd]s may bg ^ affected> 

Again the pigment may be in such excess that the tumor will 
be a black color. These tumors are very liable to have 
their elements conveyed to distant parts by the blood-veesels 
in which case their melanotic character will accompany them. 
In this way secondary growths are found in the liver, kidneys, 
lungs, etc. The laboratory is in possession of a liver three- 
fourths of which has become transformed into little melanotic 
growths, varying in size from a pea to masses two inches in 
diameter. This variety of the sarcomata is perhaps the most 
malignant of all, exceeding in this particular many of the 
cancers. 

An osteoid sarcoma is usually a spindle-celled sarcoma 
that has either become truly ossified, or more or less hardened 
by calcareous deposits. It is important to recognize the sar- 
comatous element, inasmuch as the innocence or malignancy 
of the growth will depend upon it. Some acid, as dilute hy- 
drochloric, may be used to dissolve out the calcareous matters 
when it can be examined for the characteristic cells, which, if 
found, will decide its malignancy. 

Figure 179 shows the large and small round cells oi a sar- 
coma, growing in the orbit after enucleation. This tumor re- 



26'2 THE STUDENTS' MANUAL OF HISTOLOGY. 

curred after removal, causing the death of the patient. A sar- 
coma composed of round cells is usually of much softer con- 
sistence than one composed of spindle cells. Such a sarcoma 
© %>t» is composed of true embryonic connec- 

^5) £§1*3^ (Ilk live tissue, with a fine granular inter- 
S^^t ,B, 9 cellular substance. The smallest cells 
®CN^ o *%£V ta -ke carmine staining evenly, evidently 
©8^** consisting of nothing but free nucleus 

c , r . . .: . matter. The larger cells have a 

FIG. 179. Large and small round & 

ceils frorr. sarcoma of orbit. nucleus while the largest have frequent- 

ly two nuclei, with nucleoli. The cut surface yields a juice 
rich in cells. This variety increases with a rapid growth by 
invading the healthy surrounding structures, involving the 
lymphatics and internal organs. It is full of blood-vessels 
easily ruptured. It is not to be mistaken for encephaloid 
cancer, which it resembles by physical characters. Here 
the cells are of a nearly uniform size and character, and 
there is an entire absence of an alveolar stroma. When an 
alveolar stroma is present careful attention must be given to 
notice whether the cells are grouped together in these alveolar 
spaces or exist singly and alone. If the latter then it is 
termed an alveolar sarcoma, if the former, it belongs to 
one of the cancers. It is often very difficult to distinguish be- 
tween the two. Figure 177 illustrates the large many nu- 
cleated cells of the myeloid sarcoma. This variety is usually 
found growing in connection with bone, especially from the 
medullary cavity. The nuclei vary in number from two or five 
to ten or fifty. These large cells are generally separated from 
each other by a number of cells of the spindle-shaped variety, 
among which are seen a few round or oval ones. It is quite 
frequently encapsuled, most frequent in early life, and is the 
least malignant of all the sarcomata. 

Thus it will be seen that all the sarcomata possess malig- 
nant properties, in this respect ranking next the cancers. 



THE STUDENTS MANUAL OF HISTOLOGY. 



263 



They disseminate by means of the blood-vessels, and thus 
rarely infect the lymphatics, a clinical distinction between 
these growths and the cancers, marked and distinct. For this 
reason they are reproduced with greater rapidity than the 
cancers. The lung being the most favorite seat for the secon- 
dary growths. No one variety of the sarcomata is necessarily 
malignant, while again the same variety may recur in the same 
place many times. 

THE CARCINOMATA. 

A cancer is a growth consisting of a fibrous, alveolar 
stroma, the meshes of which are filled with cells of an epi- 
thelial type. While the cells have no " specific " character, 
yet they are recognized by their large size, irregular shape, 
the prominence, number and size of their nuclei and nucleoli. 
These cells exhibit every possible shape, as seen in figure 181. 
They are full of granular matter and from their great liability 
to undergo fatty degeneration they usually contain some fat 
globules. In the juice of the cancers will be found numerous 
free nuclei, especially in the younger and softer growths. Cells 
not very unlike these are found in the normal tissues or in 
those tissues when slightly inflamed. The day of the " specific 

cancer cell " is nearly over, in 
fact there is no such thing at 
the present time, the very best 
pathologists hold strictly that 
" every pathological growth 
has its physiological proto- 
type." 

If cells are found in a 
fig. .80. stroma of Scirrhus. growth of the character de- 

scribed above and illustrated at figure 181, then that growth 
must be looked upon with suspicion, but before pronouncing 
jt a cancer two other things must be carefully noted; first, the 




264 THE STUDENTS' MANUAL OF HISTOLOGY. 

stroma, and second, the arrangement of the cells within the 
alveoli. The stroma, or solid portion of the cancer generally 
consists of a frame-work of connective tissue as seen at figure 
180, so arranged that round or oval alveoli are formed freely 
communicating with one another, in which are grouped to- 
gether the cells described above. The amount of stroma varies 
exceedingly. Sometimes it is so great as to form the largest 
part of the tumor. The alveolar spaces are then very small, 
and the growth will be hard to the touch, and the cut surface 
will yield but little juice. Again it may be very scanty as in 
the rapid growing and young cancers. Every possible degree 
as to quantity exists. Cancers have been found in all tissues 
save cartilage. The female mammae, uterus, lower lip, stom- 
ach, liver, oesophagus and lymphatic glands are all favorite 
places for the development of the cancers. They may occur 
alone or in great number, and appear as tumors or as infil- 
trations. They are very rarely separated from the healthy 
tissues surrounding them by a capsule, but on the contrary 
show a close connection with them. 

The blood-vessels are arranged very different from those 
found in the sarcomata. In the latter it will be remembered 
the vessels ramify all through the growth, and their walls be- 
ing composed of embryonic connective tissue, they easily rup- 
ture and then the elements are easily and rapidly disseminated. 
While in the former — the cancers — 
the blood-vessels course within the 
stroma and very rarely indeed do 
they communicate with the alveoli. 
Thus, it is very rare, if ever, that the 
cancers are disseminated by means 
of the blood-currents. However a 
fig. 181. Ceils from scirrhus. study of the lymphatics shows them 
to be numerous, accompanying the blood-vessels and com- 
municating freely with the alveoli spaces. The elements thus 




THE STUDENTS' MANUAL OF HISTOLOGY. 265 

enter the lymphatics readily and are carried to the nearest 
glands where they are caught in its meshes and are carried 
further on, not however until the gland itself has become suf- 
ficiently affected to furnish other elements. In the cancers, 
then, dissemination is slow and accomplished through the 
lymphatics. All cancers are very liable to undergo fatty me- 
tamorphosis, especially the young -and rapidly growing vari- 
eties. 

Scirrhus or chronic cancer, as its name implies, is of slow 
growth and of a firm and hard structure. In this variety the al- 
veoli are small and comparatively poor in cells. Instead of the 
organs affected being increased in size they are many times 
actually reduced, often depressed in the centre and firmly at- 




FIG. 182. Stroma of encephalo 



tached to the skin. A microscopical examination of the centre 
of this growth may reveal nothing but cicatricial tissue. The 
cells have suffered degeneration, while the stroma has atro- 
phied and contracted. At the periphery will be found a zone 
of cells, and free nuclei infiltrating the neighboring tissues. 
Between the two will be seen the characteristic alveolar stroma 
as at figure 180, together with the cells as at figure 1S1. Its 
most frequent seat is in the female mammae and in the 



2 66 



THE STUDENTS MANUAL OF HISTOLOGY. 



stomach. The secondary growths arising from it are generally 
encephaloid. 

Encephaloid or acute cancer differs from the above mostly 
in its rapid growth and small amount of stroma. It is usually 
very soft and by scraping the fresh cut surface an abundance 
of juice is given off, rich in cells, free nuclei, granular matter, 
etc. Figure 182 illustrates the stroma smaller, and the alve- 
olar spaces correspondingly larger than found in scirrhus. It 
is not of so frequent occurrence as scirrhus, arising as a 
secondary growth of the latter. 

By colloid is understood a degeneration of the above 
varieties. A section of colloid shows a small amount of stroma 




FIG. 18&. Colloid. 

and nearly entire absence of cells. The alveolar spaces are 
quite well marked, being generally round, varying in size, and 
filled with the soft, colorless, glistening colloid material, in 
which are a few cells. Many times the cells themselves appear 
filled with this same material. 

Epithelioma or cancroid varies much according to its- 
situation. Arising from the cutaneous or mucous surface the 
cells will be found to correspond with the cells taken from 
those surfaces. Like those found on these surfaces they are 
usually irregular in shape, containing generally one nucleus, 



THE STUDENTS MANUAL OF HISTOLOGY. 



267 



sometimes two nuclei. Their arrangement is most peculiar 
and characteristic. They appear to arrange themselves in 
groups and thus they form the " concentric globes " or " epi- 
thelial nests." These nests are frequently so large as to be 
visible with the naked eye, especially when they are of a yel- 
lowish color from becoming hard and dry. The epithelium is 
here heterologous in its nature, extending from the surface 
into the subjacent connective-tissue, giving the great charac- 
teristic of this variety. The point of junction of the cutaneous 
and mucous surfaces is its favorite seat. Here on the lower 
lip it is usually seen to commence as a small ulcer, caused by 
some external irritation, which grows quite rapidly, becoming 
firm and indurated, with an ulcerating surface. Under pres- 
sure the cut surface may 
yield little worm-like curdy 
masses, such as can be 
forced from the sebaceous 
glands of the skin. By 
many authors this is con- 
sidered very characteristic. 
While all the cancers are 
highly malignant, some pos- 
fig. 184. Epithelioma. sess this property to a much 

greater degree than others. The vascular and rapidly grow- 
ing encephaloid reproduces itself in the neighboring lymphat- 
ics the most rapidly, while the chronic scirrhus is nearly its 
equal, colloid is the least so of the three. Epithelioma is by 
far the least malignant of all the cancers, in this respect rank- 
ing below some of the sarcomata. Its thorough removal is 
not likely to be followed by a return of the growth. It may 
extend, however, and infect muscle, bone, and lymphatics. It 
rarely reproduces itself in internal organs, but when it docs so 
the secondary growths correspond to the primary one. 




CHAPTER XXII. 



Starch. 

STARCH is the most generally diffused, excepting pro- 
toplasm, of all vegetable substances within the cell-wall. 
When found in the older structures, roots, stems, seeds, etc., it 
is found nearly pure; when found in freshly-growing tissue it 
is in union with chlorophyll. Starch grains contain carbon, 
oxygen, hydrogen, and some mineral matter. They are in- 
soluble in water, alcohol, ether, and oil; are destroyed by 
potassa, and colored blue or violet by iodine — the color de- 
pending on the density of the granule and the strength of the 
iodine. The starch grains of different families and different 
species of the same family differ so much in size and general 
appearance as to be easily identified. The largest starch 
grains known are those of tous-les-mois, which are frequently 
gi-Q of an inch in length, while the smallest are those of rice, 
which are occasionally t^Vo °f an mcn m diameter. 

Potato Starch. — Botanists have taken the potato-starch grain 
as the typical form with which they compare others. So we 
should have a good knowledge of this grain. If the com- 
mercial starch is not accessible, the grains can easily be obtain- 
ed by cutting a fresh potato with a clean knife, and then float- 
ing on a glass slide, with a drop of water, the white substance 
which adheres to the side of the knife. Or, shave off a very 
thin slice of the potato, and place it in a watch-crystal in a 

268 



THE STUDENTS' MANUAL OF HISTOLOGY. 269 

little water; the fine sediment settling to the bottom will be the 
starch. There are two leading theories regarding their growth. 
Some claim that the surface of the grain is formed first, and 
that it grows by layers being deposited on the inner surface of 
the case, which gradually expands until it reaches its normal 
size. The other and the more generally accepted opinion is, 
that the nucleus is formed first, and the grain grows by means 
of deposits of starchy matter around this nucleus, and each 
successive layer contains less moisture than the preceding layer; 
this explains the appearance of rings or laminae seen so plainly 




FIG. 185. Potato Starch, x 375. 

in the potato and many other starches. A new theory has 
been advanced in Sachs' Botany (page 59), which is too long, 
however, for an explanation in this connection. In specimens 
which have been subjected to even a slight degree of dry heat, 
there appears a black line or star-shaped mark over the 
nucleus. The heat evaporates the moisture from the grain, 
and. there must be a shrinkage on the surface to correspond 
with the evaporation. This is the greatest over the nucleus 
where is the greatest moisture. The grains are round, ovate, 
irregularly oval, or egg-shaped, nearly transparent; nucleus 



270 THE STUDENTS MANUAL OF HISTOLOGY, 

eccentric (not in the centre), and in the smaller end 
of the grain, and surrounded by numerous distinct rings 
or laminae. The grains are very irregular in size; the smallest 
are just perceptible, and the largest are frequently ^-g- of an 
inch in length. A very decided cross is seen when viewed 
with polarized light, the arms of the cross radiating from the 
nucleus, not from the centre of the grain. This is the cheap- 
est and the most common starch; there being from $800,000 
to $1,200,000 worth thrown on the market annually. Probably 
the greatest part is used for adulterations. 

Arrow-root Starch closely resembles potato-starch. The 
grains are much more uniform in size than those of the potato, 
and are about -g^- of an inch in length. The nucleus is gen- 
erally in the larger end of the grain, while in the potato-starch, 
as before mentioned, it is in the smaller end; while the rings 
are finer and more numerous. Thirty or forty rings can fre- 
quently be counted in one grain, while potato-starch some- 
times has only three or four. Arrow-root starch takes a dis- 
tinct cross with polarized light. It is very frequently adul- 
terated with potato starch. 

Wheat Starch. — Pure wheat starch can be obtained by cut- 
ting through a kernel of wheat, and scraping with the point of 
a knife a little from the central part of the kernel on a glass 
slide. There are two distinct kinds of grains found here; 
small spherical or angular grains floating frequently in a mass, 
many times more numerous than the large grains, and about 
g0 1 00 of an inch in diameter. The others are large, lenticular 
grains, which, when viewed on the face, appear like a spherical 
grain. When viewed on the edge, they have the appearance 
of a double-convex lens. This lens shape can easily be proved 
by touching the cover glass gently with a pencil-point, and 
watching the grains roll over in the field. This should always 
be done when testing for adulterations with starch grains. 
There is seldom any nucleus, but when it is present it is cen- 



THE STUDENT S MANUAL OF HISTOLOGY. 



271 



tral, and still more seldom are there any rings. When viewed 
with polarized light, only a faint cross is seen if any.* When 
subjected to dry heat, the grains are changed very much in ap- 
pearance; being warped considerably from their normal shape. 
They are larger, more brittle, and more transparent. Yet gen- 
erally they can be identified when subjected to either dry or 
moist heat, if the moist heat be not raised to the boiling point. 
The large grains of wheat starch in their normal state are very 
uniform in size for the same variety, but the starch-grains of 
the different varieties differ considerably in size. The average 




FIG. 186. Wheat starch. X375, 

diameter of the grain in the eight varieties examined is ir J T of 
an inch.f Barley and rye are closely related to wheat, 



All of 



* The statement is made by some botanists that wheat starch gives a cross under 
polarized light, but I have never been able to detect any closer approach to one than a 
nearly uniform shadow floating over the grain. 

f These measurements have been made with considerable care. In each case 20 
grains, as nearly typical as possible, were selected, and accurately measured; the average 
was then taken, with the following results: The largest grains of Treadwell wheat 
measured 1-861 of an inch in diameter; Deihl, 1-816; Wicks, i-S$i; Egyptian, 1-004; 
Russian, 1-1174; Clawson, 1-1256; Schaffer, 1-1000; Vienna flour, 1-861. There is also con- 
siderable difference in the size of the sma'l grains. Schaffer small grains measure 1-4700 
of an inch in diameter; Treadwell, 1-6102; Vienna flour, 1-5166; Russian, 1-4000; Egyp- 
tian, 1-6000. 



272 



TKE STUDENTS MANUAL OF HISTOLOGV. 



these are used extensively for adulterations. 

Barley Stareh is composed of large and small grains. 
The large grains are smaller than those of wheat; being about 
, i A of an inch in diameter. There is less difference between 

1 D 

the long and the short diameters than in wheat starch, so that 
when the grains are rolled over they present less of a lens- 
shape, being rounder. Rings and a star-shaped nucleus are 
quite frequently apparent. The small grains are more 
angular, frequently having a nucleus, and average g-J^- of an 
inch in diameter. No cross is seen when viewed with 
polarized light. 




FIG. 187. Bean Starch. X375. 

Rye Starch grains are larger than those of wheat, very 
seldom do they show any rings, and when present they are 
eccentric; occasionally a star-shaped and central nucleus is 
present. The large grains average y^- of an inch, the small 
grains 57 ] 17 of an inch in diameter. A distinct cross is seen in 
rye starch with the polarized light. After examining these 
starches in their natural condition, they should be subjected to 
both dry and moist heat, and examined, as their appearance is 



LHE STUDENTS MANUAL OF HISTOLOGY. 



273 



much changed by heating. As adulterants, they are frequent- 
ly so treated. 

Bean Starch. — We have here a very different appearance 
from any other starch, excepting that of the pea. The 
grains are regularly oval and quite uniform in size. A dark 
line with ragged edges generally extends the whole length of 
the grain; cross-marks being frequently seen. Faint rings are 
seen near the edge of the grain. The grains average about 
-g-Lj- of an inch in length and TT jVo of an inch in breadth. Dry 
heat renders the grains more brittle, and destroys the nucleus, 




Corn search. X375. 



but not the rings. Moist heat expands, distorts, renders more 
transparent, and destroys both rings and nucleus. 

Pea Starch is the nearest like that of bean starch. The 
grains are smaller and more slender, being generally less than 
7 1 of an inch in length. 

Corn Starch. — We come now to a starch grain bounded 
by plane faces and angles instead of curves. The grains are 
angular, have no rings, and present a round or star-shaped cen- 
tral nucleus. The average grain is ygVu" °f an nlcn m diameter. 
The shape is only slightly changed by dry heat, but is entirely 



274 



THE STUDENTS' MANUAL OF HISTOLOGY 



destroyed by moist heat. The grains found in the central or 
outer part of the kernel of corn are more angular than those 
found in the inner part. This variety is frequently substituted 
for wheat flour, under the name of " amylum." 

Rice Starch. — The starch grains of rice resemble very closely 
those of corn. They are much smaller, however; being only 
p-gig- of an inch in diameter. The grains are angular; being 
bounded by plane sides only, are without rings, and have a 
central nucleus which is either a dot, a line, or star-shaped. 
The grains are aggregated together in angular or very ir- 




Rice Starch, x 375. 

regular-shaped masses. Rice is used much more extensively 
in England as an adulterant than in America, and commercial 
rice flour is frequently adulterated with corn starch. 

Oat Starch is the nearest like that of rice, and it is quite 
difficult to distinguish between them. Oat starch is both com- 
pound and simple. The compound grains or masses are oval, 
spherical, or egg-shaped; the surface of the masses being 
smooth, while those of rice are irregular. The divisions into 
grainlets show very distinctly. The simple grainlets are larger 
than those of rice; being ^Vo °f an * ncn m diameter, and 



THE STUDENTS MANUAL OF HISTOLOGY. 



275 



bounded by one or two curved faces. They are without 
nuclei and without rings. A faint cross is seen with 
polarized light. 

Buckwheat Starch is made up of both compound 
and simple grains. The compound grains or masses are 
cylindrical or prismatic. When cylindrical, the curving surface 
is perfectly smooth, but the ends are irregular, as though they 
had been broken. These masses are very numerous and char- 
acteristic, and somewhat resemble the cell-contents of black 



®3®, 






•0O 



^6 -40 






FIG. 190. Oat Starch, x 375. 

pepper; being coarser, however than the latter. Black pepper 
is largely adulterated with buckwheat. For this reason buck- 
wheat should be compared with some of Lhe grains from the 
central part of black pepper, which can be easily obtained In- 
scraping it out with the point of a pen-knife. The grain lets oi 
buckwheat starch are like those of rice, in having a central 
nucleus and no rings, and are like those of oat, in having one 
or more curved faces. In size, they are about : , 1 lMl of an inch 
in diameter. A correct knowledge of these starches, so closely 



276 



THE STUDENTS MANUAL OF HISTOLOGY. 



related to rice, can be obtained only by faithfully comparing 
each under the microscope with starch from the latter source. 
Sago Starch is obtained from the parenchyma or pith of 
several different varieties of palms. Sago appears in market 
in a variety of forms; as pearl sago, white sago, sago flour, 
sago meal, etc. When examined with the microscope, the 
starch grains of sago appear quite large compared with those 
of the other starches. They are oval, ovate, or elliptical in 
shape; much broken, generally one extremity is rounded, and 
the other extremity, or the sides near it, appear to be clipped, 




Buckwheat Starch, x 375. 



which is due to the pressure of the adjoining starch grains. 
The nucleus is eccentric, as indicated by a dark cross or slit 
which frequently extends the length of the grain ; the surface 
is irregular or tuberculated, and marked by a few distinct 
rings, fewer than are seen in the potato-starch grain. The 
grains exhibit a faint cross when viewed with polarized light. 
The starch grains composing commercial sago are so 
changed by the process to which they are subjected before 
being ready for market, that there is little resemblance 
between them and the fresh grains. The starch grains found 



THE STUDENTS MANUAL OF HISTOLOGY. 277 

in the pearl sago are the most changed by heating. Sago is 
not used so much in this country tor an adulterant as in 
Europe. Commercial sago is frequently adulterated with po- 
tato starch, sometimes with rice. Sometimes there is an entire 
substitution of potato starch for the sago. Any adulteration 
used for sago can readily be detected by the microscope, 
by noticing the above described characteristics. 

Tapioca Starch is prepared from manioc or cassava, or, 
according to Linnaeus, from the root of Janipha Manihot. 
In the preparation of tapioca for market, the substance is sub- 
jected to a temperature of ioo degrees C, which changes the 
appearance of the starch grains very much from what they are 
in their fresh state, yet they are not entirely destroyed. The 
heat partially dissolves the jouter case of the starch grains, 
which renders tapioca slightly soluble in water. The grains 
are quite uniform in size (about 2 * 00 of an inch in diameter); 
they are round or cup-shaped, with flattenings here and there, 
due to the pressure of neighboring grains. The starch grains 
of tapioca are generally found floating in the field singly, but 
in the growing root they are found compounded of two, three, 
or four grains each. A distinct and large circular nucleus is 
seen in fresh specimens. In dried specimens the nucleus is 
marked by a distinct star or cross. Tapioca is adulterated 
with rice, sago, and potato starch. Potato flour is frequently 
prepared like pearl tapioca, and sold as such. Tapioca is used 
quite extensively in England as an adulterant, but not so much 
in America. These starches, sago and tapioca, are so much 
changed in the different commercial varieties, i.e., pearl, white, 
meal, etc., that to become well acquainted with them one 
should examine each variety carefully. An illustration or 
drawing of these in their fresh state would hardly be of value 
in identifying the starch grains as we find them in market as 
an adulterant. 

Turmeric Starch is from the rhizome of Curcuma longa, 



278 THE STUDENTS' MANUAL OF HISTOLOGY. 

and is imported principally from Southern Asia. The paren- 
chyma is packed full of starch in angular or roundish 
masses. Turmeric is used extensively as a coloring material, 
to give deeper color to the spices which have been adulterated 
with some of the flours. When a ground spice, as, for 
example, mustard, contains turmeric, even if not in large quan- 
tities, its presence can be detected by exposing the mustard to 
the light, when it will fade to a dingy yellow. Its presence 
can also be detected by treating the suspected substance with 
potassa, and if turmeric be present the substance will turn a 




FIG. 192. Turmeric Starch, x 375. 

deep yellow or brick-red color. The starch grains are quite 
uniform in size, and in shape are elliptical, oval, or like flat- 
tened discs, sometimes even truncated. The nucleus is at 
one extremity, and has the appearance of being entirely out- 
side of the grain proper. Rings quite distinct, numerous and 
uniform in density, pass around the grains like zones, and pre- 
sent a beautiful appearance in a fresh grain. Commercial 
turmeric has been heated so much in preparation for market 
that frequently the rings cannot be seen, and even the normal 



THE STUDENTS MANUAL OF HISTOLOGY. 279 



shape of the grain is lost. In the fresh state they show a de- 
cided cross or black bands with the polarized light; but this is 
seldom seen in commercial turmeric. The coloring material is 
a deep, reddish yellow, and is contained in special cells 
of the parenchyma. The starch grains are white. The 
action of iodine and potassa is the same here as with all 
starches, but sulphuric and sulphochromic acids are of perhaps 
more value in this case, for they turn the coloring matter to a 
peculiar rose-pink. In the examination of mustard, this test is 
valuable. Of the twenty specimens of mustard examined, 
during the past two years, every one contained turmeric. It is 
used to color many other spices. The turmeric of commerce 
is itself adulterated frequently with corn starch, etc. 

Ginger Starch grains are irregularly spherical, oval, or 
disc-shaped, closely resembling those of turmeric, belonging to 
the same family, Zingiberacese. The nucleus is at the extrem- 
ity, as if it were hardly a part of the grain, the rings are 
numerous and uniform. A cross is seen with polarized light. 

Much of the ginger of the market has been scalded, which 
causes the starch grains to lose their normal shape. It is diffi- 
cult then to see the rings, and the cross, which was seen with 
the polarized light, is destroyed. In examining the starch 
from the root, as found in the stores, the starch grains at the 
centre will be found to be more perlect than those taken from 
near the surface of the root.* 



♦The following references may be of value to those wishing to carry the study of 
the starches farther: Hassall's "Adulterations in Food and Medicine;" Sachs' "Botany," 
page 56 ; Souberian, "Dictionnaire des Falsifications ;" Wiesner, "Rohstoffe des Plan- 
zenreiches," pp. 239-289; Planchon, '•Determination des Drogues Simples," Vol. II., 
chap. XIII • Nageli, "Die Stiirkekorner," Zurich, 1S58, 4 , Fliickiger und Hanbury's 
4 ' Pharniacographia* ' ' 



INDEX. 



PAGE. 

Abducens nerve, nucleus of 200 

Acid, carbonic 67 

Acoustic nerve, nucleus of 200 

Adenoid tissues 47 

Adenoma .'. 258 

Adeno-myxoma 258 

Adeno-sarcoma 258 

Adipose tissue 76 

Adipose tissue, tumor of 252 

Alkaline fluids 67 

Amoeba 29, 36 

properties of 30,3! 

size of 42 

Amylum 274 

Angle of aperture 17 

definition of 18 

Angioma 257 

Aniline, blue-black 25 

red 66 

Aqueductus sylvii , 198 

Arnold, ground plexus of 181 

intermediary plexus of 181 

Arteries.... 114 

coats of 114 

commencement of 114 

termination in veins of 118 

Artery, hepatic .. 145,146 

Auerbach, plexus mesentericus of 141 



Balsam, how to remove 

Blood 

action of reagents upon 

white corpuscles of 

color of 

composition of 

corpuscles and plasma cf 

crystals of 

distribution of 

dog's and human 

in criminal cases 

methods of examining ... 

number of corpuscles in 

origin of white corpuscles of 

red corpuscles of 40, 165, : 

classes of 

color of 

composition of 

effect of carbonic acid on.. 

grave of 

medico-legal value of 

nucleus of. 43, 

number of 

origin and death of 40, 

shape of 

size of 

structure of 

superficies of 

where found 



PAGE. 

Blood- 
relative number of white 

corpuscles in 60 

total quantity of 39 

volume of 49 

white corpuscles of 35, 58, 59, 196 

Blood-corpuscles, structure of 36 

when discovered 38 

Blood-stains, how examined 55 

Blood-vessels 112 

methods of examining. .. . 119 

nerves of 81 

tumor of 257 

walls of 119 



Bone. 



36,81 



articulating surfaces of 

canaliculi of ... . 

cells of 

compact 

Haversian canals of 

lacunae of 

lamellae of 

lymph capillaries of 

marrow of 

matrix of 

methods of examining 

ossein of 

periosteum of 

Sharpey's fibres of 85 

tumor of 

Bowman, membrane of 

Brain 

blood-vessels of 

cerebellum of 

connection of different parts of... 

corpora dentati 

ependyma 

gray matter of 

layers of 

methods of examining 

Meynert's layers of 

nerve fibres of 

neuroglia of 

olivary bodies of 

projection system of 

white matter of 

Bronchi 

termination of 

Brownian movement 

Bulbus olfactorius 



7i 

82 

,84 



82 

*3 
170 

85 
Si 
87 
82 
85 

1 "4 
253 
22S 
190 
196 
200 
196 

2 00 
10 6 
198 
198 
201 
198 
100 
196 
200 

197 
[96 
taa 

1-.? 
oS 
199 



Camel's hair brushes 21 

Camera lucida 18 

Canada balsam -5 

without heat -'5 

Cancer 263 

blood-vessels of .-04 

cells of -<\> 

colloid 

83 



INDEX. 



PAGE. 

Cancer, encephaloid 261 

epithelioma 266 

lymphatics of 264 

scirrhus 265 

stroma of 264 

where found 264 

Canal, alimentary 151 

Cancroid 266 

Capillaries, in 

lymph 169 

of bone 112 

of glands 112 

of mucous membranes 112 

of nervous tissue 112 

of retina 112 

size of 112 

stomata of 113 

structure of 113 

Carcinomata, the 263 

Carmine, injecting fluid 24 

staining fluid 25, 33 

Cartilage 36, 78 

cells of 78 

cricoid 134 

deposit of lime in 79 

fibrous ,. 78 

hyaline 78, 79 

lacunar of 78, 79 

lymph channels of 79 

methods of examining 80 

of vertebrae . . 79 

reticular 78, 79 

rings of 79 

tumor of 252 

varieties of 78 

yellow-elastic 79 

where obtained 80 

Cavity, oral 102 

Cells.'. 20, 32 

adipose tissue 76 

air 124 

blood 36, 168 

bone 36, 81, 84 

cancer 263 

cartilage 36, 78 

ci'iated 63, 66 

columnar 62 

connective. tissue 73. 76 

cornea ; 231 

Deiter's 200 

Deiter's hair 224 

different forms of 32, 33 

division of 35 

epithelial ^3. 36 

fixed 73.74 

ganglion 141 

giant 247 

goblet 65, 131 

growth of 34 

increased nuclei in 35 

large and small round 262 

liver 145, i 47 

loss of 35 

lymphoid if 8 

melanotic 261 

migratory 73 

2 



PAGE. 

Cells, mobile 73 

mother 267 

mucous 131 

muscle 103, 104, 105 

multipolar ganglion 198 

myeloid 247, 260 

nerve 191 

nucleus of 34 

of cornea 231 

of gray matter 20c 

of myxoma 254 

of nails 68 

of retina 239 

of seminal tubes 206 

of taste buds 216 

of tubes of kidney 151 

olfactory 216 

parietal 137 

pathological 247 

pavement 62 

Peptic 137 

pigment 77, 78 

plasma 74 

prickle ... 214, 218 

Purkin je's 200 

Sertoli 207 

spleen pulp 42 

spindle 259 

squamous 67 

stratified 68 

structure of 36 

Cement-substance 63, 73 

Cerebral ganglia 198 

Cerebellum 198 

cortex of 200 

layers of 200 

Chamois skin 21 

Chondrin 78 

Chondroma 252 

Chromatic aberration 16 

Chyie 140, 141 

Cilia 63 

Clarke's column 192 

Colloid cancer 266 

Co'or. change of. in animals 77 

Condylomata 258 

Conjunctiva, follicles of 166 

Connective-', issue 73 

tumor of 250 

Corium 70 

Cornea, lymph capillaries of 170 

Corpora, albicantia 108 

dentati 200 

quadrigemina 198 

striata 198 

Corpuscles, of blood 40 

salivary 68 

! Corti, organ of 224 

Czermak, interglobular spaces of 93 

Dammar 26 

Defining power 17 

Degenerations 247 

Deiter's cells 200 

Deiter's hair cells 224 

i Demour. membrane of 229 



INDEX. 



PAGE. 

Dental pulp 97 

Diaphragm 102, 103, 10S 

muscle cells of 103 

work of 103 

Doyere's mourn 180 

Duct, hepatic 145 

Duodenum 137, 139 



,ar 



canals of 220 

endolymph of 220 

labyrinth of 220 

lobe of 79 

methods of examining. 226 

middle and outer 102 

modiolus 221 

nerves of 223 

organ of corti 224 

otoliths 222 

vestibule of 220 

Electrical currents 67 

Embedding mixtures 26, 27 

Embryonic tissues, tumors of 259 

Encephaloid cancer 266 

Enchondroma 252 

Epididymis 205 

appendage to 151 

Epithelial cells 36 

Epithelioma 266 

Epithelium 66 

buccal 67 

cement-substance of 63 

ciliated 63, 66 

methods of examining 64 

pigmented 68 

squamous 67 

stratified 68 

structure of 62 

where found 66, 67 

Examining, methods of 

adipose tissue 77 

blood 56 

blood-vessels 119 

bone 87 

brain. 201 

cartilage 80 

ciliated epithelium 64 

ear 226 



eye 

for sput 

intestine 142 

kidney 160 

liver 140 

lung 125 

lymphatics 171 

muscle 106 

nerve fibres . . . 

ovary 

salivary glands 

skin 

spinal cord 

stomach 

teeth 

testis 

tongue 

tumors 



243 

fibres 120 



[ 75 



PAGE. 

Examining, white fibrous tissue 75 

yellow elastic tissue 76 

Eye, 228 

canal of Petit 241 

canal of Schlemm 230 

capsule of lens of 242 

cells of cornea of 231 

choroid 68, 232 

ciliary muscle 233 

ciliary processes 68 

cornea of 228 

hyaloid membrane of 241 

iris 68, 233 

layers of retina of 236 

lens of 241 

ligamentum iridis pectinatum of 229 

macula lutea 239 

membrana fusca 228 

methods of examining. 243 

peculiarities of, at macula lutea 240 

pupil of 234 

retina 112, 235 

sclerotic of 228 

vitreous humor of 241 

zone of Zinn 233 

Eye-piece, of microscope 14 

deep 14 

negative 14 

shallow 14 

structure 14 

Facial nerve 200 

Fascia, inter-muscular 75 

lymph capillaries of 170 

Fat, in muscle 109 

Fibres, nerve 173 

ganglionic nerve 177 

sputa 128 

termination of nerve 173 

Fibro-cellular tumor 259 

Fibro nuclear tumor 259 

Fibro-plastic tumor 259 

Fi broma 250 

Field , flat 17 

Fifth nerve, nucleus of 200 

Focussing, rule for 21 

Fossa, Sylvii 100 

Frog, lung of [23 

G^ n S ua i cerebro-spinal 178 

sympathetic 17S 

Gelatine - 1 

Gerlach's nerve net-work 193 

Gianuzzi, cells of 131 

composition of [31 



131 

.'OO 



crescents 01 

Girardes, organ of 

Glands, abdominal salivary. . . 

Brunner's 137 

during secretion 131 

lymphatic 104 

mucous 134, -•'4 

parotid I3I 

peptic 1 30 

Peyer's 

pyloric 136 



28«? 



INDEX. 



PAGE. 

Glands, salivary 130 

sebaceous 219 

serous 215 

submaxillary 131 

sudoriferous 219 

thymus 166 

Gland-tissue, tumor of 258 

Glisson, capsule of 147 

Glomeruli 155 

(jlosso-pharyngeal nerve, nucleus of... 200 

Gluten 73 

Glycerine 26 

Graafian folli les 209 

Granules, fat . 106 

pigment 157,168 

Gray matter, lining ventricles 198 

Green, classification of tumors by 249 

Hematoxylin 25 

Hair 62,69 

different layers of 69, 70, 71 

gray 69 

growth of 71 

properties of 69 

sacs of 71, 72 

size of 69 

sudden blanching of 69 

to obtain sections of 72 

Haller, vas aberrans of 206 

Heat 67 

Heart, peculiarities in structure of 98, 102, 108 

rudimentary 40 

Henle, loops of 156 

Hippocampus major 199 

Hodgkin, disease of 256 

Hypertrophy 246 



I nfundifula 

Injecting apparatus 

Injecting mixtures .23 

Intestine 134 ,138, 

examination of 

glands of 

large 

mucous membrane of.. 138, 142, 

small 

villi of 62, 

blood-vessels of 

lymphatics of .... 

number of 

valvulae conniventes of 

walls of 

Illumination 

central light 

day light 

direct light 

gas light 

north light 

oblique light 

reflected light 

sun light 



J ejunum 139 

ICebs, muscular fibrils of 181 



PAGE. 

Sidney 151 

arteriolse rectae of 159 

arterial system of 158 

Bowman's capsule of 155 

capsule of glomeruli of 155 

cells of, tubes of 157 

centro-tubular membrane of 157 

cortical portion of 154 

cortical pyramid of 154 

first trace of 151 

glomeruli of 155 

intercalary portion 156 

loops of Henle of 155 

lymphatics of 160 

Malpighian, bodies of 155, 159 

medullary portion of 154 

medullary rays of 154 

medullary substance of 153 

methods of examining 160 

nerves of 160 

papillae of 153 

physiology of 157 

shape of 152 

straight uriniferous tubes of 154 

urtiniferous canals of 155 

venous system of 159 

Wolffian bodies of 151 

Klein, neuroglia matrix of 188 

Krause, bulbs of 182 

rod ellipsoid of 237 

terminal plate of 180 

Kuehne, end plate of 180 

Lacunae 78, 79 

Langerhaus, layer of 218 

Larynx 121 

Lewis', method of preparing brain by. . .2or 

Lieberkuhn, crypts of 141, 142 

Lipoma 252 

Liver 144, 152 

arteries of 145 

bile capillaries of C47 

capillaries of 145 

cells of -. 145, 147 

ducts of 145 

early appearance of 144 

examination of 149 

injection of 150 

lobules of 1 44 

of pig 144 

relative weight of 144 

size of lobules of 144 

veins of 145 

inter lobular 145 

intra lobular 146 

walls of bile capillaries of 148 

Lung 123 

air vesicles of 124 

capillaries of 125 

first appearance of 12 r 

how inflated J23 

injection of 126 

in phthisis 128 

lobules of 124 

lymph capillaries, of 170 

methods of examining 125 



286 



INDEX. 



PAGE. 

Lung, of frog ±23 

how prepared 123 

pigmented ^7 

Lymph 43 

Lymph-capillaries 169 

Lymph-channels 79 

Lymphatic glands 164 

blood-vessels of 165 

corpuscles of 165 

cortex of 164 

course of lymph in. . . 165 

follicles of 164 

matrix of 165 

medulla of 164 

sheath of 164 

Lymphatics 162 

methods of examining 171 

puncturing method 162 

stomata of 162 

how demonstrated 163 

structure of 162 

vessels of 162 

Lymphatic-tissue, tumor of 255 

Lymphoid organs 166 

Lymphoma 255 



IVIacula iutea 

Magnifying power, how determined. . . . 

Malignancy 

Malpighian, bodies 

corpuscles 

Meissner, plexus of 

tactile corpuscles of 

Melanin 

Membrane, centro-tubular 

Membranes, lymph capillaries of 

Meynert, layers of 

Micrometers 

Microscope 

accessories to 

care of 

compound 

erector to 

eye-piece of 

names of parts of 

objective of 14, 

simple 

stands 

when in focus 

Mounting media 25 

Mucigen 

Mucin 65, 

Mucous-tissue, tumor of 

Muscle 

cells of 103, 104, 

color of 

compartments of 

contractile discs of 

discliaclasts of 

endomysium of 

fasciculus of 

fatty degeneration of 

" infiltration of 

fibres of 98, 

granular layer 



PAGE. 

Muscle, how divided 98 

interstitial discs of 100 

involuntary and unstriped 103 

Krause's membrane of.. 102 

lateral disci of 102 

longitudinal striae of ior 

lymph capillaries of 170 

myosin of 101 

nuclei of 100 

of alimentary canal 134 

perimysium of 98 

primitive fibrillar of ior 

relation to tendon of 107 

rods of 101 

sarcolemma of 99, 108 

skeletal 102 

striated, where found 102 

termination of nerve fibres in ... . 180 

transverse discs of 101 

trichinae in 107 

Muscle cells, degeneration of no 

Muscularis mucosae 135 

Muscular-tissue, tumor of 256 

Myeloid cells 259 

Myoma 256 

Mvosin 101 

Myxoma 256 

Nails 68 

Nasmyth, membrane of 96 

Neutral tint reflector 18 

Neuroma 257 

Net-work, intracellular 37 

intranuclear 36 

Nerve-fibres 173 

axis cylinder of 174 

axis fibrillae of 175 

constriction rings of 175 

different parts of 173 

division of 170 

ganglionic 177 

how divided 173 

lymph capillaries of 170 

medulla of 174 

medullated 173 

methods of examining 175 

modes of termination of 179 

non-medullated 170 

of the brain 196 

olfactory 177 

Remak's 177 

size of 173 

termination of, in conjunctiva... iS.- 

in cornea 185 

in car aa ; 

in nose 217 

in salivary glands... [3a 

in skin 184 

in striated muscle. . . . 180 

in teeth o-' 

in tendon 18.- 

in tongue ai6 

in unstri.ued muscle t8o 

Nerve-tissue, tumor of 

New formations : 



287 



INDEX. 



PAGE. 

New formations, cells of 247 

Nose, ending of nerve fibres in 217 

mucous membrane of 216 

olfactory cells of 216 

Nuchae, ligamentum 76 

Nucleus of nerves 200 

Odontoblasts 91 

Obesity 109 

(Esophagus 102, 134 

mucous membrane of 134 

muscle fibres of 134, 135 

Objectives 17 

achromatic 17 

corrected 17 

good qualities of 15 

how numbered 18 

immersion 18, 22 

structure of 15 

systems of 15 

Olivary bodies 200 

Optic nerve, nucleus of 200 

Optic thalami 200 

Organs, lymphoid 166 

Ossein 82 

Osseous tumor 253 

Osteoblasts 86 

Osteoma 253 

Ovary 209 

cortical layer of 209 

coverings of 209 

germinal layer of 209 

germinal spot 211 

germinal vesicle 211 

Graafian follicles 204 

liquor f olliculi 211 

membrana granulosa 210 

methods of examining 212 

ovum 210 

tissues of 209 

tunica albuginea 209 

tunica fibrosa 210 

Ovum 210 

Pacinian bodies 183, 219 

Pancreas 130, 132 

Papillae, tumor of 257 

Papilloma 257 

Parepididymis 206 

Penetrating power 16 

Perichondrium 78 

Petit, canal of 241 

Peyer's glands 166 

Pharynx 102, 134 

lining of 134 

mucous membrane of 134 

walls of 134 

Pigment, cells 77 

excretion of 158 

granules 68, 77 

Pigments, bile, urinary 42 

Process, vermiform 167 

Projection system, of the first order 197 

•' second order. 197 
" third " .198 



PAGE. 

Prostate, muscles of 102 

Prussian blue 23 

Pulmonary lobule 123, 124 

Puncturing, method of injecting by 167 

Purkinje, granular layer of 94 

cells of 200 

Pus 35, 59 

Reagents 23 

Rectum 102 

Recurrent fibroids 259 

Remak's fibres 177 

Ranvier, constricton rings of 175 

Respiratory passages 121 

bronchi of 121 

larynx of 121 

lungs of 123 

trachea of 122 

Retzius, brown striae of 96 

Rhomboidal fossa 198 

S aliva 67 

Salivary glands 130 

alveoli of 130 

ducts of 130 

lobes of 130 

varieties of 130 

Sankey, method of preparing brain by. 202 

Sarcoma, spindle-ceiled 259 

alveolar 262 

large and small round celled . 262 

melanotic 260 

myeloid 260 

osteoid 261 

Sarcomata, the 259 

Schlemm, canal of 230 

Schronn, cortical layer of 209 

Schwalbe, taste buds of 215 

Schultze, olfactory cell of 216 

prickle cells of 214 

Schwann, sheath of 173 

Schweigger-Seidel, middle piece of 208 

Scirrhus cancer 265 

Seminal vesicles 205 

Sertoli, cells of 207 

Sharpey, fibres of 85 

Silver staining 65 

Size of an object 20 

Skin 217 

epidermis of 217 

glands of 219 

layers of 217 

lymph-capillaries of 170 

methods of examining 226 

papillae of 218 

Spinal cord 186 

blood-vessels of 194 

cells of ,191 193 

central canal of 192 

Clarke's column of 192 

commissures of 190 

cornua of 191, 192 

course of fibres of 194 

enlargements of 187 

rissu. es of 187 



INDEX. 



PAGE. 

Spinal cord, frame-work of 188 

Gerlach's nerve net-work of 193 

gray substance of 190 

length of 186 

ligamentum denticulatum . . 186 

membranes of 186 

methods of examining 194 

neuroglia of 188 

subarachnoidean tissue of. . 186 

white substance of 188 

Spermatoblasts 207, 208 

Spermatozoa 207 

Spherical abberration 16 

Spleen 166 

blood-vessels of 169 

cells of 168 

coats of 167 

extirpation of 47, 48 

follicles of 167 

Malpighian corpuscles of 167 

Sputa, in suspected phthisis 128 

Stand, of microscope 12 

different parts of 13 

Starch 268 

arrow root 270 

barley 272 

bean 273 

buckwheat 275 

corn 273 

ginger 279 

oat 274 

pea 273 

potato 268 

rice 274 

rye 272 

sago 276 

tapioca 277 

turmeric 277 

wheat 270 

Staining— mixtures 25, 66 

Stilling, canal of 241 

Stomach 134 

blood-vessels of 138 

coats of 135 

glands of 136 

lymphatics of 138 

methods of examining 142 

mucous membrane of 135, 167 

nerves of 138 

peptic glands of 136 

peptic glands of, during digest'n 137 

pyloric glands of 137 

Substance, interfibrillar 37 

Taste-buds 215 

Teeth 90 

brown striae of enamel of 96 

cementum of 94 

cuticle of 96 

dental pulp of 97 

dentinal sheath of 93 

dentine of 93 

enamel of 95 

interglobular spaces of 93 

methods of examining 96 



Teeth, nerves of 92 

parts of 90 

pulp cavity of 91 

Tendon 73, 75 

lymph capillaries of 170 

termination of nerve fibres in 182 

Testicle 203 

coverings of 203 

development of 203 

divisions of 203 

epididymis , 205 

mediastinum of 204 

organ of Girardes 206 

rete testis of 204 

seminal tubes of 206 

seminal vesicles 205 

spermatozoa 207 

tubes of 203 

tunica albuginea 204 

vasa recta of 204 

vas aberrans of 206 

vas deferens of 205 

vasa eff erentia of 204 

Tissue, adipose 76 

connective 73 

nervous 112 

sub-cutaneous 73, 75 

white fibrous 73, 75 

yellow elastic 75 

Tongue 214 

methods of examining 204 

nerves of papillae of 216 

papillae of 215 

serous glands of 215 

taste-buds of 215 

Tonsils 167 

Trachea 122 

Trichinae 107 

size, shape of 109 

vitality of 109 

when discovered 108 

where found 107 

Tuber cinereum 198 

Tubes, fallopian 151 

Tumors 246 

cells of 247 

classification of 249 

degenerations of 247 

examination of 248 

when malignant 248 

Urine, solid constituent of 158 

water of 

Uterine fibroids 

Uterine polypus 

Uterus 106, 



V agus nerve, nucleus of . 
Valentin, membrane of. . . 

Vasa-vasorum 

Veins 

hepatic 

interlobular 

intralobular 

portal 

Vermiform process 



i57 
256 
256 
'5i 

200 
171 
no 
«S 

MO 
M5 
MO 

45 

167 



2S9 



INDEX. 



PAGE. 

Vesicae, sphincter 102 

Vesical, prostatic 151 

Villous tumor 257 



Wolffian bodies, purpose of. 

size of 

structure of. 
Working distance 



yN aldeyer, germinal layer of 20Q 

Warts 258 i T ellow elastic tissue 



White fibrous tissue 73 

effects of reagents on 73 

Wolffian bodies 151 

disappearance of 152 



structure of . . 
where found. 



Xinn, zone of 233 



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